fidzu : Mozilla

I've spent a lot of time at Mozilla working on session history, the machinery that keeps track of where you've been so the back and forward buttons do something sensible. It's one of those parts of the browser that sounds simple from the outside and turns out to be anything but. Once you add iframes, nested iframes, and the subtle rules about when a navigation creates a new entry versus replacing the current one, the state you're reasoning about gets large and hard to hold in your head.

For years my main tool for understanding that state was reading code and printing things to a log. That works, but it's slow, and it never quite shows you the shape of the thing. So I built a way to see it: a new DevTools panel in Firefox Nightly called Session History Diagrams. It lives under the Application tab, next to Service Workers and Manifest, and it draws the browser's session history as a diagram that updates as you navigate.

Jake diagrams

I didn't invent the idea of drawing this. The HTML spec already has a notation for it, called a Jake diagram after Jake Archibald, and that's where I started. It's a tabular notation where columns represent steps in session history, and rows represent navigables (the top-level browsing context plus any iframes). Background colors identify documents, a fresh color marking a new document loaded in that navigable, and the current step is shown in bold. It's a genuinely useful way to capture multi-navigable interactions that are otherwise hard to describe in prose.

These diagrams don't have to be drawn by hand. Domenic Denicola, one of the HTML spec editors, built a Jake diagram generator that turns a description of a navigation sequence into a rendered diagram. That's where I first started playing with a more dynamic approach to the visualization. The thing I missed the most was being able to build a history up step by step rather than describe a finished sequence all at once. So I wrote rejake, a small tool that draws diagrams in the same style¹, but lets you construct the history one step at a time.

But rejake, like the spec's diagrams and Domenic's generator before it, was stuck with a limitation the spec itself admits to, that they only work with a single level of nesting. That was exactly my problem. Real pages nest iframes inside iframes, and the bugs I was chasing usually lived down in that deeper nesting, precisely where the diagram stops being able to help. And however I drew them, I was still typing the history out by hand. It's a short step from there to wanting the diagram to draw itself from the browser's actual session history instead².

Firefox Session History Diagrams

So the panel extends Jake diagrams to handle arbitrary nesting. Every column is a step in the session history. Every row is a frame, listed in pre-order from the frame tree: top-level document first, then its first iframe, then that iframe's children, and so on. The current entry is highlighted in blue, and the diagram updates live as you navigate.

The recording above is an ordinary bit of browsing, a handful of pages visited one after another. The top row tracks the page you're actually looking at, and the current position is the one in blue. The interesting part is everything underneath that top row.

Some of those pages didn't just load a single document. They pulled in nested frames of their own, and the diagram stacks those below the page that owns them. None of that is visible in the address bar or anywhere in the page chrome, and the frames come and go as you move through the history. Normally you'd have no way of knowing they were ever there. Here you can read straight off the diagram which frames a given step carried, when each one entered, and when it dropped away again.

Who else might want this

I built this for myself, working on Gecko's session history internals, where being able to watch the diagram change while reproducing a bug turns opaque state into something I can point at. But it turns out I'm not the only one who hits this wall. Plenty of people working elsewhere in Gecko, anywhere near navigation, end up reasoning about the same state, and now we all share one picture of it.

If you build single-page applications, or work with the History API or Navigation API, you've probably run into the same kind of confusion from the other side. A push where you expected a replace, a missing history entry, an iframe that accumulated entries unexpectedly. These are hard to reason about without seeing the state directly, and that's exactly what the diagram gives you.

Session history isn't a Firefox-specific problem either. Every engine implements the same part of the HTML spec, and Jake diagrams come from that shared spec. The panel only ever shows Firefox's state, but the rules are the same everywhere, so if you work on another engine it can still be a useful reference for how one implementation behaves. It's often the only practical way to surface an interoperability difference, which might be a bug in any of the engines, but stays hidden until you can actually see it.

Enabling it

The panel is available in Firefox today, behind a pref. It's been there in some form since Firefox 150, growing more stable with each release. To turn it on, set devtools.application.sessionHistory.enabled to true in about:config, then reload DevTools and open Application → Session History.

Since Firefox 153 it also works over remote debugging. Connect to a device from about:debugging and you can watch the session history of a page running on Android, the same as you would on the desktop.

Thanks

A big thanks to Nicolas Chevobbe, whose assistance was invaluable in getting the DevTools integration right. The work, including what's still to come, is tracked in Bug 2015726. There's a fair bit still on that list, like marking whether a step was a push or a replace, surfacing back/forward cache state, tying the diagram into the Network and Inspector panels, and more, all heading toward fuller DevTools support for Navigation and Session History.

Notes

01 Jun 2026 12:00am GMT

Like many, docker and and compose have become my go-to tool to create software that can be conveniently deployed to production with a limited amount of headache. However, many tasks, and sometimes whole services, pertain only to the development side of the workflow, and need to stay there.

Moreover, some tasks, such as time-consuming provisioning tasks, are only on-demand one-offs. They shouldn't run at all most of the time, but they should slot into the dependency graph correctly when needed.

tl;dr: I realised that docker compose supports profiles, which allows services to be enabled conditionally, along with the depends_on.[].required option, to ignore them when they are disabled. Profiles are also useful to package actions and triggers to run on demand, so they are not started by default.

We can start with a simple setup where our long-running main service depends on an init service to perform preliminary steps. This can be setup with depends_on the compose.yaml.

services:
  main:
    image: debian:latest
    command: "sh -c 'while : ; do echo main; sleep 10; done"
    depends_on:
      init:
        condition: service_completed_successfully

  init:
    image: debian:latest
    command: sh -c 'echo init; sleep 10'

Even when run ning the main container, we get the right dependency (and delay). So far so good (though up will show the output from all containers.

But what if we have another, much more time consuming, initialisation step?

services:
   [...]
   opt-init:
    image: debian:latest
    command: sh -c 'echo opt-init; sleep 100'

Perhaps we are lucky, and while it needs to run once, we don't need it to run everytime (think: database setup).

Docker compose can use profiles to select when services are started. It will then only be started when this profile is selected. Services without explicit profile will always be started, but any service with one or more profile listed will only get started iff that profile is selected.

We can make the opt-init service part of the opt profile. We can also make the main service dependent on it, so it is started beforehand.

services:
  main:
    [...]
    depends_on:
      [...]
      opt-init:
        condition: service_completed_successfully

  opt-init:
    [...]
    profiles:
      - opt

This works well enough when the opt profile is specified but… Oh no! If the profile is not specified, the dependency on the opt-init isn't resolvable, and none of the stack can spin up with just docker compose up

Fortunately, this is easily solved with the required attribute of the depends_on objects.

services:
  main:
    [...]
      opt-init:
        condition: service_completed_successfully
        required: false

And that's really all there is to it: with the right profile, the optional dependency is started in the desired order, but its absence is otherwise transparently ignored. Both docker compose up and docker compose --profile opt work as desired.

Profiles afford us another useful trick: on-demand tasks not started by default. This can be handy for maintenance tasks (data cleanup, garbage collection, …) or test scripts (running test workload, sending message, …). Those are handy during development, but would not be necessary, or take a different form, in other deployments.

services:
  [...]
  say-hello:
    image: debian:latest
    profiles:
      - hello
    command: echo hello
    depends_on:
      main:
        condition: service_started

Conveniently, when explicitly running a service, it is not necessary to request a matching profile, keeping the command line lean: docker compose run say-hello.

So here we are. Compose profiles allow us to control which services get started, and mark some as conditional. This, coupled with the ability to mark some depends_on rules as not required is a good way to seamlessly prevent heavy or otherwise time consuming services from starting when not needed, while retaining proper dependency ordering when enabled.

For completeness, the full, final, compose.yaml looks as follow.

services:
  main:
    image: debian:latest
    command: "sh -c 'while : ; do echo main; sleep 10; done'"
    depends_on:
      init:
        condition: service_completed_successfully
      opt-init:
        condition: service_completed_successfully
        required: false

  init:
    image: debian:latest
    command: sh -c 'echo init; sleep 10'

  opt-init:
    image: debian:latest
    profiles:
      - opt
    command: sh -c 'echo opt-init; sleep 100'

  say-hello:
    image: debian:latest
    profiles:
      - hello
    command: echo hello
    depends_on:
      main:
        condition: service_started

The post Optional Docker services and dependencies first appeared on Narf.

31 May 2026 11:58am GMT

Servo 0.2.0 contains all of the changes we landed in April, which came out to yet another record 534 commits (March: 530). For security fixes, see § Security.

We've shipped several new web platform features:

• <select multiple> (@lukewarlow, @mrobinson, #43189)
• <template shadowrootslotassignment> (@simonwuelker, #44246)
• <video> playback on OpenHarmony (@rayguo17, #43208)
• 'minimum-scale' and 'maximum-scale' values in <meta name=viewport> (@shubhamg13, #40098, #43715)
• 'color-mix()' with any number of <color> values (@Loirooriol, #43890)
• '&::before' and '&::after' in '::details-content' (@Loirooriol, #43878)
• 'revert-rule' (@Loirooriol, #43878)
• 'tab-size' (@mrobinson, @SimonSapin, #44480)
• 'text-align: match-parent' (@TG199, #44073)
• new Worker() with blob URLs (@jdm, #44004)
• get­Context("webgl") on Offscreen­Canvas (@niyabits, #44159)
• the detail property on Performance­Mark and Performance­Measure (@shubhamg13, #44289, #44272)

Plus a bunch of new DOM APIs:

• 'selectionchange' events on <input> and <textarea> (@TimvdLippe, #44461)
• Storage­Manager, in experimental mode (@Taym95, #43976)
• active­Element on Document and Shadow­Root (@mrobinson, #43861)
• crypto.subtle.supports() (@kkoyung, #43703) - Servo is the first major browser engine to support this!
• cell­Padding, cell­Spacing, and align properties on HTML­Table­Element (@mrobinson, #43903) - previously supported in HTML only
• related­Target on 'focus' and 'blur' events (@mrobinson, #43926)
• transfer­From­Image­Bitmap() on Image­Bitmap­Rendering­Context (@Messi002, #43984)

Servo's support for text in Chinese, Japanese, and Korean languages has improved, with correct wrapping in the layout engine (@SharanRP, #43744), and CJK fonts now enabled in servoshell's browser UI on Windows, Linux, and FreeBSD (@yezhizhen, @CynthiaOketch, @nortti0, #44055, #44138, #44514).

Navigating to a JSON file as the top-level document now renders the JSON with an interactive pretty-printer (@webbeef, @TimvdLippe, #43702).

April was a big milestone for Servo, with some automated tests failing because they had hard-coded cookie expiry dates set to April 2016 plus ten years. Surprise! We're still here. Here's to the next 100 years of Servo (@jdm, #44341).

This is another big update, so here's an outline:

• Security

• Work in progress

• servoshell

• For developers

• Embedding API

• More on the web platform

• Performance and stability

Security

Crypto­Key now zeroes buffers containing key material after use (@kkoyung, #44597).

With only a few exceptions, you can only access DOM APIs in another document if that document is in the same origin. But if that document is in the same site with a different port number, Servo currently allows these accesses even though it shouldn't. We've fixed some (but not all) of these incorrect accesses, specifically those that involve binding a Window or Location method in this document with a this from the other document (@yvt, @jdm, #28583).

We've fixed a bug where local­Storage and session­Storage were usable in sandboxed <iframe> and shared with every other sandboxed <iframe>, rather than throwing Security­Error (@Taym95, #44002).

We've fixed a bug where local­Storage and session­Storage were shared between all <iframe srcdoc> documents, rather than isolated using the origin of the containing document (@niyabits, #43988, #44038).

We've fixed a bug where IndexedDB was usable in sandboxed <iframe> and data: URL web workers (@Taym95, #44088).

We've fixed a bug where pages in some IP address origins can evict cookies from other IP address origins (@officialasishkumar, #44152). Only evicting cookies was possible, not reading or writing them.

We've fixed an out-of-bounds memory read in tex­Image3D() on Web­GL2­Rendering­Context (@simartin, #44270), and fixed some undefined behaviour in servoshell's signal handler (@Narfinger, #43891).

Work in progress

IndexedDB is now enabled in servoshell's experimental mode (@arihant2math, #44245). As always, embedders can enable it with Preferences::dom­_indexeddb­_enabled (@arihant2math, #44245, #44283).

IndexedDB now uses Servo's new "client storage" system, which is based on the Storage Standard and will allow us to have a unified on-disk format and quota management for all web platform features that persistently store data (@gterzian, #44374, #43900). We've also made key range queries more efficient (@arihant2math, #39009), landed improvements to IDB­Database, IDB­Object­Store, IDB­Cursor, IDB­Key­Range, IDB­Request, and to the handling of transactions, keys, values, and exceptions (@Taym95, #44128, #43901, #44009, #43914, #44161, #44183, #44059, #44215, #42998, #43805).

We've made more progress on the Intersection­Observer API, under --pref dom­_intersection­_observer­_enabled (@stevennovaryo, @jdm, #42204).

We're continuing to implement document.exec­Command() for rich text editing (@TimvdLippe, #44529), under --pref dom­_exec­_command­_enabled. This release adds support for the 'bold', 'font­Name', 'font­Size', 'italic', 'strikethrough', and 'underline' commands (@TimvdLippe, @jdm, @mrobinson, #44511, #43287, #44432, #44410, #44194, #44030, #44039, #44041, #44075, #44234, #44250, #44331, #44390, #44137, #44293, #44312, #44347).

All of the features above are enabled in servoshell's experimental mode.

Servo can now build a very basic accessibility tree for web contents, under --pref accessibility­_enabled (@alice, @delan, @lukewarlow, #42338, #43558, #44437, #44438). This includes text runs, plus nine other non-interactive accessibility roles (@alice, @delan, #44255). We've also fixed a crash when reloading pages with accessibility enabled (@alice, #44473), and made accessibility tree updates more efficient (@alice, #44208).

We've started implementing the Sanitizer API, under --pref dom­_sanitizer­_enabled (@kkoyung, #44198, #44290, #44335, #44421, #44452, #44481, #44585, #44594).

We've also started implementing Shared­Worker, under --pref dom­_sharedworker­_enabled (@Taym95, #44375, #44440).

We're working on the Wake­Lock API too, under --pref dom­_wakelock­_enabled (@TG199, @rovertrack, #43617, #44343).

servoshell

servoshell for Android now has a revamped browser UI, including a new history view (@espy, #43795), the apk is 30% smaller (@jschwe, #44278, #44182), and we've fixed the black screen bug when closing settings or switching back from another app (@yezhizhen, #44327). You can now close tabs on OpenHarmony too (@Narfinger, #42713).

As for servoshell on desktop platforms, we've fixed some focus- and IME-related bugs (@mrobinson, #43872, #43932), and on Windows, we now install a normal shortcut without the strange behaviour of an "advertised" shortcut (@yezhizhen, #44223).

For developers

When using the Inspector tab in the Firefox DevTools, the Rules panel now includes declarations in '@layer' rules (@arabson99, #43912).

When logging expressions in the Console tab, and when hovering over symbols in the Debugger tab, you can now get more information about the contents of functions, arrays, objects, and other values (@atbrakhi, @eerii, #44172, #44173, #44022, #44233, #44196, #44181, #44064, #44023, #44164, #44369, #44262).

When using the Debugger tab, you can now use the Scopes panel to inspect local and global variables (@eerii, @atbrakhi, #43792, #43791), you can now debug web worker scripts (@atbrakhi, #43981), and we've started implementing blackboxing, aka the Ignore source button (@freyacodes, #44142).

We've also landed some initial support for the Style Editor tab (@rovertrack, #44517, #44462).

We're working towards re-enabling our automated DevTools tests in CI, which should make the feature more reliable (@freyacodes, #44577), and we've landed a small build reproducibility fix too (@jschwe, #44459).

For developers of Servo itself, please note that the Cargo 'release' profile is no longer #[cfg(debug­_assertions)] (@jschwe, @mrobinson, #44177). If you've been using 'release' as a "faster 'debug' with assertions" build locally, consider switching to 'checked-release' or 'medium'.

The pull request template has been updated (@mrobinson, #44135). 'Testing' and 'Fixes' should go at the bottom of the PR description, and 'Testing' is about automated tests, not how you tested the PR locally.

We've made more progress on the new dev container, which will provide an alternative to our usual procedures for setting up a Servo build environment (@jschwe, @sagudev, #44126, #44111, #44162, #44641, #44109). Keep an eye out for that in the book!

In the meantime, did you know that you can use Lix or Nix to build Servo on Linux with a lot less hassle, even if you're not using NixOS? For now at least, head to the NixOS page in the book to learn more. We've also fixed a regression that made --debug-mozjs and MOZJS­_FROM­_SOURCE builds take much longer to complete on Linux when not using Nix (@jschwe, #44346).

We've fixed building Servo with the 'jitspew' feature in mozjs, allowing you to set IONFLAGS to enable JIT logging (@simonwuelker, #44010). We've also fixed build issues on Windows and FreeBSD (@zhangxichang, @mrobinson, #44264, #44591).

Embedding API

With this second monthly release of the Servo library, we have some quick notes about API stability and semver compatibility:

• The 'servo' package follows Cargo's rules for semver compatibility. 0.1.1 is compatible with version 0.1.0, but 0.2.0 is a breaking update.

• Until we integrate semver analysis into our release process, each monthly release will have a breaking version number, while non-breaking version numbers may be used for LTS updates.

• In general, dependencies of 'servo', like 'servo-base' and 'servo-script', do not use semver. Any release may include breaking changes.

We've fixed a build failure affecting embedders with a new or updated Cargo.lock (@jschwe, #44093), and landed several other changes to help us with the Servo library release process (@jschwe, @mukilan, #43972, #44642, #43182, #43866, #44086, #43797).

Breaking changes:

• Web­View::animating now takes &self instead of self, so you can call it without cloning the handle (@JavaDerg, #44253)

• Servo::site­_data­_manager now returns &SiteDataManager instead of Ref<'_, SiteDataManager> (@sabbCodes, #44116)

• Web­View­Delegate::play­_gamepad­_haptic­_effect and stop­_gamepad­_haptic­_effect have been removed (@mrobinson, #43895), but they have not worked since February 2026 - use Gamepad­Delegate instead

You can now load a URL with custom request headers by calling Web­View::load­_request (@Narfinger, @longvatrong111, @mrobinson, #43338).

You can now retrieve cookies asynchronously by calling Site­Data­Manager::cookies­_for­_url­_async (@longvatrong111, #43794).

The synchronous version of that method, Site­Data­Manager::cookies­_for­_url, was previously not callable because Cookie­Source was not exposed to the public API, but we've fixed that now (@TG199, #44124).

You can now clear session cookies without clearing permanent cookies by calling Site­Data­Manager::clear­_session­_cookies (@longvatrong111, #44166).

When intercepting requests with Servo­Delegate:: and Web­View­Delegate::load­_web­_resource, we now include a destination and referrer­_url in the Web­Resource­Request, which can be helpful if you're implementing ad blocking (@webbeef, #44493).

You can configure Servo to write all of its storage to a unique directory for that session by enabling Opts::temporary­_storage (@janvarga, #44433). Note that these unique directories currently persist after Servo exits, so it's an isolation feature, not a privacy feature.

Window­Rendering­Context::new and Software­Rendering­Context::new now return an error if the given size is less than 1x1 (@freyacodes, @mrobinson, #44011).

We've improved our API docs for Web­View, Web­View­Builder, Web­View­Delegate, ServoDelegate, Prompt­Dialog, Web­Resource­Load, Web­Xr­Registry, Preferences, and servoshell's EXPERIMENTAL­_PREFS (@simonwuelker, @TG199, @sabbCodes, @jdm, @rovertrack, #43892, #43787, #44171, #43947).

We've also improved our API docs for Opts, Output­Options, Diagnostics­Logging, Pref­Value, servo::opts, and servo­_config (@mukilan, #43802).

More on the web platform

Tab navigation now works across <iframe> boundaries (@mrobinson, #44397), and Ctrl+Backspace (or ⌥⌫) now deletes a whole word in input fields (@mrobinson, #43940).

Tab characters are now rendered correctly in <pre> (and other elements with 'white-space: pre'), with proper tab stops (@mrobinson, @SimonSapin, #44480). Spaces are now rendered correctly in 2D <canvas>, instead of twice as wide as they should be (@mrobinson, #43899).

<a href> now correctly resolves the URL with the page encoding (@sabbCodes, #43822).

We've improved the default appearance of <input type=file> (@sabbCodes, #44496) and <textarea placeholder> (@mrobinson, #43770).

All keyboard events, mouse events, wheel events, and pointer events, other than 'pointerenter' and 'pointerleave', now bubble out of shadow roots (@simonwuelker, @webbeef, #43799, #44094). 'error' events on Window now report the correct filename (source in onerror) and lineno (@Gae24, #43632).

console.log() and friends now support printf-style formatting directives, although for now %c is ignored (@TG199, #43897).

file: URLs are now considered secure contexts, so they can now use features like crypto.subtle and crypto.random­UUID (@simonwuelker, #43989).

Exception messages have improved in Location, Static­Range, and the HTML­Element family of types (@arihant2math, @MuhammadMouostafa, @treetmitterglad, #44282, #43260, #43882).

We've improved the conformance of fetch algorithms (@yezhizhen, #43970, #43798), focus and tab navigation (@mrobinson, #43842, #44029, #44360, #43859, #44535), form submission (@TG199, #43700), JS modules (@elomscansio, @Gae24, #43741, #44179, #44042), page navigation (@TimvdLippe, #43857), <svg view­Box> (@yezhizhen, #44420), 'attr()' (@Loirooriol, #43878), ':focus' (@mrobinson, #43873), 'font' (@RichardTjokroutomo, #44061), '@keyframes' (@simonwuelker, #43461), '@property' (@Loirooriol, #43878), 'load' events (@jdm, @arabson99, #43807, #44046), fetch­Later() (@TimvdLippe, #43627), axes and buttons on Gamepad (@log101, @rovertrack, #44411, #44357), copy­Tex­Image­2D() on Web­GL­Rendering­Context (@simartin, @mrobinson, #43608), tex­Image3D() on Web­GL2­Rendering­Context (@simartin, #44367), environment­Blend­Mode on XR­Session (@msub2, #44155), mark() and measure() on Performance (@shubhamg13, @simonwuelker, #44471, #44199, #43990, #43753), and Performance­Resource­Timing (@shubhamg13, #44228).

We've fixed bugs related to console logging (@sabbCodes, #44243), 'animation' (@mrobinson, #44299), 'box-shadow' (@yezhizhen, #44474, #44457), 'display: contents' (@Loirooriol, @mrobinson, #44551, #44299), 'display: inline-flex' (@SimonSapin, #44281), 'display: table-cell' (@Loirooriol, #44550), 'display: table-row-group' (@Veercodeprog, #43674), 'overflow-x: clip' and 'overflow-y: clip' (@Messi002, #43620), 'position: absolute' on grid items (@nicoburns, #44324), 'word-spacing: <percentage>' (@sabbCodes, #44031), remove­Child() on Document (@rovertrack, #44133), and URL.revoke­Object­URL() (@simonwuelker, @jdm, #43746, #43977, #44035).

Performance and stability

We've fixed some big inefficiencies in Servo. append­Child() with nested shadow roots is no longer $O\left(2^n\right)$ (@yezhizhen, @webbeef, #44016), and we've halved the time it takes to load the ECMAScript spec by fixing the $O\left(\text{whole DOM tree}\right)$ processing of 'id' and 'name' attributes (@simonwuelker, #44120, #44127, #44117).

Servo makes its first TLS connection in each session 30-60 ms faster (@jschwe, #44242), and we've instrumented the Servo and servoshell startup processes to find more opportunities for optimisation (@jschwe, #44443, #44456).

Like most browser engines, Servo is a multi-threaded (and sometimes multi-process) system requiring a great deal of IPC messages to keep everything connected. Two key components of this system are the constellation thread, which manages the engine as a whole, and the script threads (or web processes), which render the web pages. Sending these messages can be expensive though, so to reduce unnecessary IPC traffic, we've landed an optimisation that allows script threads to selectively receive only the relevant messages from the constellation (@webbeef, #43124).

We've reduced the memory usage of each Attr, Text, and Character­Data node in the DOM by 16 bytes (@mrobinson, @Loirooriol, #44074), and fixed a memory leak when deleting <video controls> or <audio controls> (@Messi002, #43983).

Our about:memory page is more accurate now too, with new tracking of libc memory allocations on macOS, improved tracking of libc memory allocations on Linux (@jschwe, #44037), and more accurate tracking of Path­Buf and types in tokio, http, data­_url, and urlpattern (@Narfinger, #43858).

Less memory usage isn't always better in browser engines though, because there are many kinds of caches and other optimisations we can do to make browsing the web faster, at the expense of increased memory usage. For example, we can greatly speed up prototype checks for DOM objects by storing a number in each object that identifies the concrete type, at the expense of making each DOM object 64 bits larger (@webbeef, #44364).

Layout can now reuse fragments in later reflows, in many cases that involve block layout or 'position: absolute' (@mrobinson, @lukewarlow, @Loirooriol, #42904, #44231). We're also working on reusing shaping results in later reflows, and making inline layout more efficient (@mrobinson, #44370, #43974, #44436).

We've landed several changes that should reduce the binary size of Servo (@rovertrack, @mrobinson, @nicoburns, @Narfinger, #44227, #44221, #44303, #44338, #44428, #44134).

We've also reduced clones, allocations, borrow checks, GC rooting steps, and other operations in many parts of Servo (@rovertrack, @Narfinger, @Loirooriol, @yezhizhen, @simonwuelker, #44008, #44544, #44271, #44279, #43826, #44052, #44139).

Several crashes have been fixed:

• in compressed­Tex­Sub­Image2D() on Web­GL­Rendering­Context (@thebabalola, #44050)
• in console.log() (@thebabalola, #43844)
• in get­Data() on Data­Transfer (@SimonSapin, #44607)
• in remove() on Element (@SimonSapin, #44435)
• in replace­With() on Element (@yezhizhen, #44503)
• in --debug-mozjs builds (@jdm, #44386, #44573, #44581)
• in flex and grid layout (@mrobinson, @nicoburns, #44424, #44203)
• in layout queries like offset­Height (@mrobinson, #44560)
• in the devtools Debugger tab, when stepping and when inspecting nested values (@atbrakhi, @eerii, #44024, #43995)
• when removing <colgroup> from the DOM (@Loirooriol, #43846)
• when running garbage collection (@drasticactions, #43933)
• when running servoshell with a u64 --pref (@yezhizhen, #44079)
• when shadow roots are deeply nested, or when calling attach­Shadow() removes elements from the flat tree (@yezhizhen, @mrobinson, #43888, #43930, #44259)
• when web storage features fail to write to disk or encounter SQLite errors (@arihant2math, @sabbCodes, #43918, #43949)

We fixed a crash in servoshell when pressing keys like Ctrl+2 or ⌘2 with not enough tabs open (@mrobinson, #44070).

DOM data structures (#[dom­_struct]) can refer to one another, with the help of garbage collection. But when DOM objects are being destroyed, those references can become invalid for a brief moment, depending on the order the GC finalizers run in. This can be unsound if those references are accessed, which is a very easy mistake to make if the type has an impl Drop. To help prevent that class of bug, we're reworking our DOM types so that none of them have #[dom­_struct] and impl Drop at the same time (@willypuzzle, #44119, #44501, #44513).

We've improved our static analysis for GC rooting (@officialasishkumar, #44489), and we've continued our long-running effort to use the Rust type system to make certain kinds of dynamic borrow failures impossible (@sagudev, @TimvdLippe, @Narfinger, @elomscansio, @Gae24, @rovertrack, @yezhizhen, @nodelpit, #43174, #43524, #43928, #43943, #43942, #43944, #43946, #43952, #43975, #44018, #44175, #44241, #44368, #44406, #44441, #44422, #44475, #44478, #44484, #44476, #44490, #44477, #44494, #44497, #44498, #44495, #44505, #44506, #44507, #44508, #44509, #44510, #44512, #44482, #44527, #44528, #44531, #44534, #44542, #44533, #44543, #44553, #44547, #44563, #44562, #44565, #44558, #44583, #44606, #44605, #44608, #44602, #44584, #44620, #44590, #44254, #44628, #44629, #44638, #44626, #44081).

Thanks to a wide range of people, we've also landed a bunch of cleanups and refactors (@delan, @alice, @Skgland, @atbrakhi, @eerii, @sabbCodes, @jdm, @thebabalola, @CynthiaOketch, @kkoyung, @TimvdLippe, @rovertrack, @webbeef, @arabson99, @yezhizhen, @simonwuelker, @mrobinson, @nicoburns, @longvatrong111, @niyabits, @treetmitterglad, @foresterre, @mukilan, @elomscansio, @freyacodes, @StaySafe020, @TG199, #43772, #44006, #43860, #44121, #44160, #43884, #44154, #44569, #43939, #44003, #44110, #44122, #43824, #44635, #44103, #43978, #44092, #44114, #44277, #44454, #44274, #44237, #44232, #44167, #44214, #43820, #43825, #43810, #43838, #43841, #43847, #43875, #43876, #43889, #43893, #43896, #43881, #43906, #43913, #43908, #43917, #43910, #43921, #43924, #43925, #43907, #43923, #43916, #43909, #43911, #43957, #43969, #43967, #43915, #43954, #43963, #43959, #43955, #44067, #44068, #44071, #44084, #44265, #44115, #44358, #43848).

Donations

Thanks again for your generous support! We are now receiving 7349 USD/month (+2.5% from March) in recurring donations. This helps us cover the cost of our speedy CI and benchmarking servers, one of our latest Outreachy interns, and funding maintainer work that helps more people contribute to Servo.

Servo is also on thanks.dev, and already 33 GitHub users (−4 from March) that depend on Servo are sponsoring us there. If you use Servo libraries like url, html5ever, selectors, or cssparser, signing up for thanks.dev could be a good way for you (or your employer) to give back to the community.

We now have sponsorship tiers that allow you or your organisation to donate to the Servo project with public acknowlegement of your support. If you're interested in this kind of sponsorship, please contact us at join@servo.org.

Use of donations is decided transparently via the Technical Steering Committee's public funding request process, and active proposals are tracked in servo/project#187. For more details, head to our Sponsorship page.

31 May 2026 12:00am GMT

This is a blog post about standards, their proliferation and the issues that may arise. My first involvement with standards was just as a reader. To better understand complicated code or unexpected behavior in a protocol. After a while, I also got involved and helped clarify certain things to ensure implementations align on the same behavior in edge cases. Eventually, I found myself co-editing a specification - Subresource Integrity (SRI) which was published as a W3C Recommendation in 2015. The core idea behind SRI is that you include third-party JavaScript combined with a SHA2 digest of the expected file. If the browser does not find the downloaded URL to match the expected digest, the script will not execute. This allows using a fast CDN for JavaScript without giving them full control over the scripts on your page - essentially reducing the security risks.

The standard format for these digests is e.g., sha(size)-(base64 encoding of the digest). While computing the hash digest is rather straightforward, base64 comes in two encoding alphabets: First, a-zA-Z0-9/+ and secondly the url-safe variant which uses a-zA-z0-9_-. The specification examples all used the former.

Only approximately ten years after publication, in 2025, we still found a bug. As part of a compatibility report against Firefox not properly supporting a website, we found that the core issue was actually with a different browser. The other browser liberally accepted both types of encoding, which resulted in websites expecting support for base64 and base64url interchangeably. The page did not work in Firefox, because it did not accept all hashes a website wanted the browser to check, revealing a minor security issue.

The real fix would have been that the standard clarifies that the base64url variant is incorrect and the other browser engine changes their behavior.

But due to (somewhat unrelated) issues around proliferation of standards, web compatibility and the unfortunate market dominance of certain browsers, we went the other road. To support existing web content, we changed the standard to acknowledging that both types of encoding are considered valid representations.

This example shows, that it can take multiple years for subtle differences to appear. Interoperable specifications can establish a shared understanding along a "happy path", but not necessarily in adversarial settings. In addition, standards need to continuous maintenance and active stakeholders who ensure that implementations remain interoperable and secure over time.

From specification to standard

Originally, a specification is at first just a write-up, an idea how something could be better: How it should behave, how it works, what the data structures, the algorithms and the interactions of them look like. Anyone can come up with a grammar, a parser and a resulting data structure.

For a standard, this specification needs a shared agreement that is also widely and consistently implemented. This will work best with iterative co-design of the spec, the implementations and intense discussions of corner cases. Some may go further and use shared test suites.

This will lead to Interoperability (interop), but still requires constant maintenance and observation of the ecosystem beyond individual implementations. While interop is asymptotic and requires a shared agreement over time, security demands understanding - a broader reach that requires the inspection of limitations and subtle boundaries.

This deeper level of understanding is often missing when implementations consider syntax "simple enough" without reading the spec. The base64 SRI example is just one example, but there are more:

Many people have written their own parsers for text-based languages. You may have seen code that parses HTML with regular expressions. Other great examples of "easily" parsed languages are maybe XML, JSON, or YAML.

But these implementations often make different assumptions, leading to subtle incompatibilities or even security flaws.

Parser Differentials

More practical, let's look at an issue with JSON, to demonstrate the impact of handling input that is ostensibly simple. Let's examine this JSON string and the resulting data structure:

{
    "test": 0,
    "test": 1
}

When parsed into an object obj, what do you think will obj.test return? Most JSON parsers are so liberal that they will happily consume two dictionary keys with the same name "test". One implementation may simply assign obj.test twice: First with 0 and then overwrite it with 1. Another one might check for existing keys and reject the second "test" key silently, keeping the first one.

The lack of rigor in the original description of JSON as a "subset of JavaScript" was already acknowledged and raised as problematic in the JSON RFC (which came much later in 2017). But still to this day, many implementations allow input with duplicate dictionary keys and show divergent behavior.

While the examples with SRI and JSON are relatively harmless, real parser differential bugs were leading to code execution, authentication bypasses and more¹.

What do we learn from this?

Perfect interoperability is not created through a specification, it needs constant maintenance. The ambiguity can only be removed through long-term commitment and regular feedback from implementations and users.

The same is true for security: The SRI bug persisted for ten years and nobody noticed how implementations disagreed and corner cases were overlooked. They only aligned due to a real, user-facing issue.

But these examples are not a warning sign, they are scar tissue that shows how the internet is made. Standards can only mature through vigilant maintenance.

The bug reports, the spec issues being filed, the shared test cases, sometimes even the random forum complaints. All of these help to remove ambiguity and allow internet standards to mature.

In the end, standards are not secure because they are written down. They are secure because people continue to question, understand, and maintain them.

30 May 2026 10:00pm GMT

The Rust team is happy to announce a new version of Rust, 1.96.0. Rust is a programming language empowering everyone to build reliable and efficient software.

If you have a previous version of Rust installed via rustup, you can get 1.96.0 with:

$ rustup update stable

If you don't have it already, you can get rustup from the appropriate page on our website, and check out the detailed release notes for 1.96.0.

If you'd like to help us out by testing future releases, you might consider updating locally to use the beta channel (rustup default beta) or the nightly channel (rustup default nightly). Please report any bugs you might come across!

What's in 1.96.0 stable

New Range* types

Many users expect Range and related core::ops types to be Copy, but this is not the case: they implement Iterator directly, and it is a footgun to implement both Iterator and Copy on the same type so this has been avoided. RFC3550 proposed a set of replacement range types that implement IntoIterator rather than Iterator, meaning they can also be Copy. The standard library portion of that RFC is now stable, introducing:

• core::range::Range
• core::range::RangeFrom
• core::range::RangeInclusive
• Associated iterators

A Rust version in the near future will also add core::range::RangeFull and core::range::RangeTo as re-exports from core::ops (these do not implement Iterator and already implement Copy), and core::range::legacy::* as the new home for the current ranges. Range syntax like 0..1 still produces the legacy types for now, but will be updated to core::range types in a future edition.

With these stabilizations, it is now possible to store slice accessors in Copy types without splitting start and end:

use core::range::Range;

#[derive(Clone, Copy)]
pub struct Span(Range<usize>);

impl Span {
    pub fn of(self, s: &str) -> &str {
        &s[self.0]
    }
}

The new RangeInclusive also makes its fields public, unlike the legacy version which avoided exposing the exhausted iterator state. This isn't a concern with the new type since it must be converted to begin iteration.

Library authors should consider making use of impl RangeBounds in public API, which accepts both legacy and new range types. If a concrete type is needed, prefer using new ranges as this will eventually become the default.

Assert matching patterns

The new macros assert_matches! and debug_assert_matches! check that a value matches a given pattern, panicking with a Debug representation of the value otherwise. These are essentially the same as assert!(matches!(..)) and debug_assert!(matches!(..)), but the printed value improves the possibility of diagnosing the failure.

These new macros have not been added to the standard prelude, because they would collide with popular third-party crates that provide macros with the same name. Instead, they should be manually imported from core or std before use.

use core::assert_matches;

/// [Random Number](https://xkcd.com/221/)
fn get_random_number() -> u32 {
    // chosen by a fair dice roll.
    // guaranteed to be random.
    4
}

fn main() {
    assert_matches!(get_random_number(), 1..=6);
}

Changes to WebAssembly targets

WebAssembly targets no longer pass --allow-undefined to the linker which means that undefined symbols when linking are now a linker error instead of being converted to WebAssembly imports from the "env" module. This change prevents modules from linking unless all linking-related symbols are defined to catch bugs earlier and prevent accidental issues with symbol naming or similar.

Undefined linking-related symbols are often indicative of build-time related bugs or misconfiguration. If, however, the old behavior is intended then it can be re-enabled with RUSTFLAGS=-Clink-arg=--allow-undefined or by editing the source code and using #[link(wasm_import_module = "env")] on the block defining the symbol.

This change was previously announced on this blog, and now takes effect in Rust 1.96.

Stabilized APIs

• assert_matches!
• debug_assert_matches!
• From<T> for AssertUnwindSafe<T>
• From<T> for LazyCell<T, F>
• From<T> for LazyLock<T, F>
• core::range::RangeToInclusive
• core::range::RangeFrom
• core::range::RangeFromIter
• core::range::Range
• core::range::RangeIter

Two Cargo advisories

Rust 1.96 contains fixes for two vulnerabilities for users of third-party registries.

• CVE-2026-5223 is a medium severity vulnerability regarding extraction of crate tarballs with symlinks.

• CVE-2026-5222 is a low severity vulnerability regarding authentication with normalized URLs.

Users of crates.io are not affected by either vulnerability.

Other changes

Check out everything that changed in Rust, Cargo, and Clippy.

Contributors to 1.96.0

Many people came together to create Rust 1.96.0. We couldn't have done it without all of you. Thanks!

28 May 2026 12:00am GMT

The latest version of PerfCompare is now live!

Check out the change-log below to see the updates:

[kala-moz]:

• Bug 2036968: Replaced fast-kde with fftkde and used bootstrap-ci to get CI summary (#1034)

• Bug 1931291: Created expand all rows functionality (#1037)

• Bug 2032246: Add cles statement to expanded row (#1033)

• Bug 2037551: Reduced the size of perfcompare hero on Results Page (#1036)

[padenot]: Use SJ bandwidth for top-level results, ISJ for subtests

[shtrom]: Bug 2014041: add support for landoInstance QueryString parameter (#1038)

Thank you for the contributions!

Bugs or feature requests can be filed on Bugzilla. The team can also be found on the #perfcompare channel on Element. Come and chat!

1 post - 1 participant

Read full topic

27 May 2026 9:29pm GMT

Hello and welcome to another issue of This Week in Rust! Rust is a programming language empowering everyone to build reliable and efficient software. This is a weekly summary of its progress and community. Want something mentioned? Tag us at @thisweekinrust.bsky.social on Bluesky or @ThisWeekinRust on mastodon.social, or send us a pull request. Want to get involved? We love contributions.

This Week in Rust is openly developed on GitHub and archives can be viewed at this-week-in-rust.org. If you find any errors in this week's issue, please submit a PR.

Want TWIR in your inbox? Subscribe here.

Updates from Rust Community

Newsletters

• Scientific Computing in Rust #18 (May 2026)

Project/Tooling Updates

• gitoxide - May 26
• hyper User Survey 2025 Results
• Rust Update: gRPC Welcomes Tonic!
• serde-const-default v0.1: Removes boilerplate when using const values as field defaults
• BoquilaHUB 0.5: AIs for Nature. Now it includes SOTA AI bioacoustics models and embeddings models
• splog: a log viewer TUI with automatic tag categorization
• rgx v0.12.3 - Building a regex debugger for the terminal in Rust
• UI tests are the guardrails an AI needs: the story of clipboardwire
• slintcn 0.22: shadcn/ui-style copy-paste components for Slint native apps
• Releasing dtact v0.2.2 and rssn-advanced v0.1.0: the next generation async concurrent engine and scientific computing engine

Observations/Thoughts

• Noroboto: Lying Fonts and Mitigation in Rust
• Erasing Existentials
• libwce: the entropy layer of a wavelet codec, on its own
• Tech Notes: Theseus: translating win32 to wasm
• Bevy Game Engine Explained Visually
• The reflex of deriving serde traits
• Physical AI Needs a Typed World Model, Not a Vector DB
• Keep calm and use (Rust) monorepos
• [audio] Rust for Linux Live with Alice Ryhl and Greg Kroah-Hartman
• [audio] Netstack.FM episode 38 - Building and testing network stacks with Rama
• [video] Can a QR code be made of stars?

Rust Walkthroughs

• Rust Patterns & Engineering How-Tos
• Laissez-Faire Errors
• Learn Rust HashMap and Iterators by Building a Git Object Store Reader
• Learn the Basics of Bevy by Building and Deploying Pong to Itch.io
• The Slowdown That Doesn't Show Up in Profiles
• Building an AsyncIO executor for the 3DS
• [video] Nine Ways to do Inheritance in Rust, a Language without Inheritance

Miscellaneous

• Content-addressed Rust builds (or, what kache actually caches)

Crate of the Week

This week's crate is inline_tweak, a crate to embed tweakable constants inside your Rust application without full recompilation.

Thanks to Kill The Mule for the suggestion!

Please submit your suggestions and votes for next week!

Calls for Testing

An important step for RFC implementation is for people to experiment with the implementation and give feedback, especially before stabilization.

If you are a feature implementer and would like your RFC to appear in this list, add a call-for-testing label to your RFC along with a comment providing testing instructions and/or guidance on which aspect(s) of the feature need testing.

No calls for testing were issued this week by Rust, Cargo, Rustup or Rust language RFCs.

Let us know if you would like your feature to be tracked as a part of this list.

Call for Participation; projects and speakers

CFP - Projects

Always wanted to contribute to open-source projects but did not know where to start? Every week we highlight some tasks from the Rust community for you to pick and get started!

Some of these tasks may also have mentors available, visit the task page for more information.

• rust cookbook - Expand Command Line section with clap derive, subcommands, and env vars

If you are a Rust project owner and are looking for contributors, please submit tasks here or through a PR to TWiR or by reaching out on Bluesky or Mastodon!

CFP - Events

Are you a new or experienced speaker looking for a place to share something cool? This section highlights events that are being planned and are accepting submissions to join their event as a speaker.

• No Calls for papers or presentations were submitted this week.

If you are an event organizer hoping to expand the reach of your event, please submit a link to the website through a PR to TWiR or by reaching out on Bluesky or Mastodon!

Updates from the Rust Project

352 pull requests were merged in the last week

Compiler

• rustc_on_unimplemented: introduce format specifiers
• account for proc macro spans in do_not_recommend diagnostics
• implement fast path for derive(PartialOrd) when deriving Ord
• make bitset would_modify_words more vectorzer-friendly
• parse mut restrictions
• stop needing materialized places for most intrinsics

Library

• add unstable Share trait
• stabilize bool_to_result
• use strongly typed wrapped indices in VecDeque

Cargo

• compiler: forward verbose flag to rustc for local crates
• don't use the network for a publish dry-run test
• break out RegistryConfig and crate_url for interpreting RegistryConfig::dl
• fix CVE-2026-5222 and CVE-2026-5223
• artifact: remove compat mode from artifacts

Rustdoc

• stabilize --remap-path-prefix in rustdoc

Clippy

• useless_format: fire on wrapped in a block-producing macro
• return can be removed from the last stmt of a block if it has an expr
• add check for midpoint using multiplication by 0.5 and >> 1
• avoid unnecessary String allocations in MinifyingSugg arithmetic ops
• extend clippy::missing_safety_doc to unsafe fields
• fix manual_range_contains NAN handling
• fix error message for useless_borrows_in_formatting for mutable borrows
• move unnecessary_get_then_check to complexity
• simplify is_some() && …unwrap() to is_some_and in unit_arg

Rust-Analyzer

• diagnostics: mut_ref binding feature diagnostic
• assists/add_reference_here: _modify_ the reference type when dealing with &T->&mut T
• cfg: correct separator index in CfgDiff disable loop
• hir-ty: saturate float-to-uint cast in const eval
• test-utils: drain inactive_regions by inactive_line_region
• add diagnostic for E0033
• add diagnostic for E0608
• completions imports exclude supports sub items
• filter package-scoped features
• extract_module missing import for macro calls
• add type_match score for struct_pat
• allow wildcard params in foreign fn declarations
• analysis expected ty in enum variant
• autoimport enum variants
• do not autoref in method probe in path mode
• do not complete semicolon in match-expr place
• do not consider the path of the macro in a macro call to be inside a macro call
• emit diagnostic for rest array patterns without fixed-length arrays
• fix SyntaxContext::roots technically overlapping valid interneds
• flip coerce_never type_mismatch tys
• have a specific error for unimplemented builtin macros
• no suggest ref match when expected generic ref
• no use sad pattern on happy arm with guard
• normalize expected tuple struct pat field
• refactor handling of generic params in hir::Type
• support named consts in range pattern types
• use grouped annotation for add_label_to_loop
• provide better incrementality for modules

Rust Compiler Performance Triage

This week was largely positive, with most of the improvements coming from algorithm change in visibility checking: #156228.

Triage done by @panstromek. Revision range: 281c97c3..783eb8c8

Summary:

2 Regressions, 2 Improvements, 5 Mixed; 2 of them in rollups 34 artifact comparisons made in total

Full report here

Approved RFCs

Changes to Rust follow the Rust RFC (request for comments) process. These are the RFCs that were approved for implementation this week:

• Propose the concept of a crates.io username for identity

Final Comment Period

Every week, the team announces the 'final comment period' for RFCs and key PRs which are reaching a decision. Express your opinions now.

Tracking Issues & PRs

Compiler Team (MCPs only)

• Promotes 5 Thumb-mode bare-metal Arm targets to Tier 2
• Add -Z dead-fn-elimination to skip codegen of BFS-unreachable functions

Rust

• Update transmute_copy to ub_checks and ?Sized
• Tracking Issue for NEON dot product intrinsics
• Never break between empty parens

Rust RFCs

• Avoid linting unreachable_code on todo!()

Unsafe Code Guidelines

• What are the values of a union type? (in particular, what is the validity invariant of a union)

No Items entered Final Comment Period this week for Cargo, Language Team, Language Reference or Leadership Council. Let us know if you would like your PRs, Tracking Issues or RFCs to be tracked as a part of this list.

New and Updated RFCs

• No New or Updated RFCs were created this week.

Upcoming Events

Rusty Events between 2026-05-27 - 2026-06-24 🦀

Virtual

• 2026-05-27 | Virtual (Girona, ES) | Rust Girona
  • Weekly coding session
• 2026-06-02 | Virtual | libp2p Events
  • rust-libp2p Open Maintainers Call
• 2026-06-02 | Virtual (Tel Aviv-yafo, IL) | Rust 🦀 TLV
  • ‎שיחה חופשית ווירטואלית על ראסט
• 2026-06-03 | Virtual (Indianapolis, IN, US) | Indy Rust
  • Indy.rs - with Social Distancing
• 2026-06-04 | Virtual (Berlin, DE) | Rust Berlin
  • Rust Hack and Learn
• 2026-06-04 | Virtual (Nürnberg, DE) | Rust Nuremberg
  • Rust Nürnberg online
• 2026-06-04 | Virtual (Tel Aviv-yafo, IL) | Code Mavens 🦀 - 🐍 - 🐪
  • Exploring FalkorDB - Learning to use a Graph Database in Rust
• 2026-06-06 | Virtual (Kampala, UG) | Rust Circle Meetup
  • Rust Circle Meetup
• 2026-06-07 | Virtual (Dallas, TX, US) | Dallas Rust User Meetup
  • Rust Deep Learning: First Sunday
• 2026-06-09 | Virtual (Dallas, TX, US) | Dallas Rust User Meetup
  • Second Tuesday
• 2026-06-10 | Virtual (Girona, ES) | Rust Girona
  • Weekly coding session
• 2026-06-16 | Virtual (Washington, DC, US) | Rust DC
  • Mid-month Rustful
• 2026-06-17 | Hybrid (Vancouver, BC, CA) | Vancouver Rust
  • Jiff
• 2026-06-17 | Virtual (Girona, ES) | Rust Girona
  • Weekly coding session
• 2026-06-18 | Hybrid (Seattle, WA, US) | Seattle Rust User Group
  • June, 2026 SRUG (Seattle Rust User Group) Meetup
• 2026-06-18 | Virtual (Berlin, DE) | Rust Berlin
  • Rust Hack and Learn
• 2026-06-21 | Virtual (Dallas, TX, US) | Dallas Rust User Meetup
  • Rust Deep Learning: Third Sunday
• 2026-06-23 | Virtual (Dallas, TX, US) | Dallas Rust User Meetup
  • Fourth Tuesday
• 2026-06-23 | Virtual (London, UK) | Women in Rust
  • Lunch & Learn: What the heck are monads - and how do we fake them in Rust

Asia

• 2026-06-02 | Beijing, CN | Voice AI and Rust Meetup (Rust for AI, lowcoderust.com)
  • AI Agents and Open Source LLM (Call for Speakers)

Europe

• 2026-05-28 | Copenhagen, DK | Copenhagen Rust Community
  • Rust meetup #68
• 2026-05-28 | London, UK | Rust London User Group
  • LDN Talks May Community Showcase
• 2026-05-29 | Berlin, DE | Rust Berlin
  • Rust Berlin Talks: The next generation
• 2026-05-30 | Stockholm, SE | Stockholm Rust
  • Ferris' Fika Forum #26
• 2026-06-02 | Frankfurt, DE | Rust Rhein-Main
  • gRPC with Rust and Tonic
• 2026-06-03 | Dublin, IE | Rust Dublin
  • Join us live and INPERSON for Rust 261
• 2026-06-03 | Girona, ES | Rust Girona
  • Rust Girona Hack & Learn 06 2026
• 2026-06-10 | München, DE | Rust Munich
  • Rust Munich 2026 / 2 - Hacking Evening
• 2026-06-11 | Switzerland, CH | PostTenebrasLab
  • Rust Meetup Geneva
• 2026-06-12 - 2026-06-14 | Kraków, PL | Rustmeet
  • Rustmeet
• 2026-06-16 | Leipzig, DE | Rust - Modern Systems Programming in Leipzig
  • Interactive: Everything is Open Source
• 2026-06-16 | Milano, IT | Rust Language Milan
  • Real-time planning in Rust: SolverForge & SERIO
• 2026-06-18 | Aarhus, DK | Rust Aarhus
  • Talk Night at Danske Commodities

North America

• 2026-05-27 | Austin, TX, US | Rust ATX
  • Rust Lunch - Fareground
• 2026-05-28 | Atlanta, GA, US | Rust Atlanta
  • Rust-Atl
• 2026-05-28 | Los Angeles, CA, US | Rust Los Angeles
  • Rust LA: Rust in Embedded & Autonomous Systems at Parallel Systems in DTLA
• 2026-05-28 | Mountain View, CA, US | Hacker Dojo
  • RUST MEETUP at HACKER DOJO
• 2026-05-30 | Boston, MA, US | Boston Rust Meetup
  • Central Cambridge Rust Lunch, May 30
• 2026-06-04 | Saint Louis, MO, US | STL Rust
  • Testing, Coverage, Tracey & Mutations
• 2026-06-06 | Boston, MA, US | Boston Rust Meetup
  • Boston Common Rust Lunch, June 6
• 2026-06-11 | Lehi, UT, US | Utah Rust
  • Utah Rust June Meetup
• 2026-06-11 | Mountain View, CA, US | Hacker Dojo
  • RUST MEETUP at HACKER DOJO
• 2026-06-11 | San Diego, CA, US | San Diego Rust
  • San Diego Rust June Meetup - Back in person!
• 2026-06-16 | San Francisco, CA, US | San Francisco Rust Study Group
  • Rust Hacking in Person
• 2026-06-17 | Hybrid (Vancouver, BC, CA) | Vancouver Rust
  • Jiff
• 2026-06-18 | Hybrid (Seattle, WA, US) | Seattle Rust User Group
  • June, 2026 SRUG (Seattle Rust User Group) Meetup
• 2026-06-24 | Austin, TX, US | Rust ATX
  • Rust Lunch - Fareground
• 2026-06-24 | Los Angeles, CA, US | Rust Los Angeles
  • Rust LA: Rust-Based Constraint Solvers in 2D Sketching with Zoo Technologies

South America

• 2026-06-18 | Florianópolis, BR | Rust SC
  • Rust Floripa

If you are running a Rust event please add it to the calendar to get it mentioned here. Please remember to add a link to the event too. Email the Rust Community Team for access.

Jobs

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Quote of the Week

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27 May 2026 4:00am GMT

The latest version of the Firefox Profiler is now live! Check out the full changelog below to see what's changed:

Highlights:

• [Markus Stange] Use @streamparser/json if the input is too large to fit in a V8 string (#6016)
• [Nazım Can Altınova] Include --search option in pq filter push (#6026)
• [fatadel] Translate URL track-index state through profile sanitization (#6000)
• [Nazım Can Altınova] Print also the status output right after cli load command (#6019)

Other Changes:

• [fatadel] Remove unused dependencies from package.json (#6010)
• [Nazım Can Altınova] Make profiler-cli work in sandboxed environments (#6003)
• [Markus Stange] Make profiler-edit run profile compacting before writing out the file (#6015)
• [Markus Stange] Migrate from prettier to oxfmt (#5986)
• [Markus Stange] Add a --symbolicate-wasm arg to profiler-edit. (#6008)
• [Markus Stange] Build and upload the cli artifact in PRs (#6020)
• [Nicolas Chevobbe] Update devtools-reps to 0.27.7 (#6030)
• [Markus Stange/fatadel] Make withSize use a wrapper element so that it can stop calling findDOMNode (#5988)
• [Markus Stange] Fix dhat importer (#6036)
• [Nazım Can Altınova] Annotate inlined frames in CLI call trees and stacks (#6041)
• [Nazım Can Altınova] Use proper types in cli tests instead of custom inline types (#6038)
• [Nazım Can Altınova] Fix text truncation for frames named after Object.prototype methods (#6044)
• [Nazım Can Altınova] Add missing key props to CodeErrorOverlay error list items (#6047)
• [depfu[bot]] Update oxfmt to version 0.51.0 (#6054)
• [Nazım Can Altınova] Sync: l10n → main (May 26, 2026) (#6058)
• [Nazım Can Altınova] Use URL-state symbol server for profiler-cli function annotate (#6051)
• [Nazım Can Altınova] Bump profiler-cli version to 0.2.0 (#6059)

Big thanks to our amazing localizers for making this release possible:

• fr: YD
• sr: Марко Костић (Marko Kostić)
• tr: Ali Demirtaş
• zh-CN: Olvcpr423
• zh-CN: wxie

Find out more about the Firefox Profiler on profiler.firefox.com! If you have any questions, join the discussion on our Matrix channel!

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26 May 2026 3:53pm GMT

You felt it. The shift. That your role has fundamentally changed thanks to LLMs. It first entered your subconscious when you realized how easily you can now crank out PRs. You felt it more concretely (and less enthusiastically), as a reviewer when you opened your laptop one morning and noticed your review queue was double what it normally is thanks to everyone else cranking out PRs. And you feel this pervasive, general sense of friction.

It's difficult to pinpoint exactly where this friction is coming from. Depending on the repository size and CI setup, it will be slightly different for everyone. It might involve longer review times or slipping review standards. You might be noticing more merge conflicts and merge related CI failures. Perhaps there are more failures sneaking through to main or CI is taking longer to give you results. You almost certainly feel the grind. People are on edge, tired; developers are pulling in opposite directions.

Here's what LLMs shifted. The bottleneck is no longer producing code. The bottleneck is integrating it. The friction we're feeling is a result of more PRs, more ideas, more reviews, more disagreements all made possible thanks to LLMs. In short, the problem can best be summarized by Figure 1:

But we're living in a moment where many folks haven't realized this yet, and are still under the impression that their job is to produce code.

It's not. Your new job is to integrate it.

26 May 2026 1:50pm GMT

Disruptions to internet connectivity can occur in countless ways - from weather incidents, natural disasters and accidents to intentional interferences like cyberattacks and government-issued blackouts. Yet while some disruptions are unavoidable, deliberate shutdowns represent a fundamentally different and deeply concerning trend. They undermine the open, global nature of the internet and put the safety, security, and fundamental rights of millions at risk.

For over 25 years, Mozilla has worked to ensure that the internet remains a global public resource-open, accessible, and safe for all. This vision, grounded in the Mozilla Manifesto, holds that the internet must remain a shared, decentralized infrastructure that empowers individuals, supports civic participation, and enables economic opportunity. Internet shutdowns run counter to these principles by restricting access, concentrating control, and weakening the very foundations of the open web.

To help organizations study and document outages, Mozilla makes aggregated Firefox telemetry data available to help identify and understand connectivity disruptions. As 2026 progresses, this data continues to show significant outages affecting millions of people worldwide-many of them the result of deliberate restrictions.

As of late May, Iran's internet blackout had been in place for over 80 days, making it the longest shutdown since the Arab Spring. Following an earlier shutdown amid nationwide protests in January 2026, Iranian authorities have restricted access to the internet since 28 February. This has meant that, for almost three months, millions of Iranians have been cut off from news, communication, work, education, and basic services. It also means that almost no independent information about the situation in Iran is leaving the country, making it almost impossible for humanitarian organizations to assess the situation on the ground. The shutdown has also had a massive impact on the Iranian economy, severely disrupting financial activity and blocking international transactions. Although Iran's president has recently ordered an end to the shutdown, it is unclear how and when Iranians will be able to reconnect to the web.

When large numbers of Firefox users experience connection failures for any reason, this produces an anomaly in the recorded telemetry data. At the country or city level, this can provide a corroborative signal of whether an outage or intentional shutdown occurred. Our telemetry documents the magnitude of the latest outage in Iran. The graph below documents the effect of the outage in multiple ways, such as users' country location, language and timezone.

Across the globe, governments are increasingly interfering with and limiting access to connectivity. Both the number of states limiting connectivity and the amount of internet shutdowns has been growing steadily. In 2025 alone, 313 shutdowns across 52 countries have been documented, a sad record. This is a stark indication that shutdowns and restrictions are no longer a rare emergency measure, but established levers of control.

While the triggers for shutdowns are varied, access to the internet continues to be blocked especially often in times of conflict and political unrest. Especially in the context of hostilities, political tensions or public health emergencies, access to connectivity is a basic humanitarian need.

Beyond their immediate human impact, blackouts also affect the internet itself. Local networks depend on each other to form the global internet, and local restrictions affect the resilience and reliability of the web at large. When governments deliberately disrupt connectivity, they do not only isolate populations; they also contribute to the fragmentation of the global internet, undermining trust, interoperability, and the stability of shared infrastructure. Over time, this erosion risks replacing a single, open web with a patchwork of disconnected or controlled networks.

Governments should foster the health of the internet, not erode it. Access to the internet is widely recognized as essential for enjoying human rights. It is an integral part of modern life, facilitating education, communication, collaboration, business and entertainment. Preserving the open web requires sustained commitment: resisting shutdowns, promoting transparency, and reinforcing the technical and governance frameworks that keep the internet global, interoperable, and accessible. The internet's value-as a platform for opportunity, innovation, and human connection-depends on it remaining open to all.

The post Growing darkness: Against the rise of internet shutdowns appeared first on Open Policy & Advocacy.

26 May 2026 8:04am GMT

The Rust Security Response Team was notified that Cargo incorrectly handled symlinks inside of crate tarballs downloaded from third-party registries, allowing a malicious crate to override the source code of another crate from the same registry.

This vulnerability is tracked as CVE-2026-5223. The severity of the vulnerability is medium for users of third-party registries. Users of crates.io are not affected, as crates.io forbids uploading crates containing any symlink.

Overview

When building a crate, Cargo extracts its source code in a local cache (stored within ~/.cargo), reusing it for any future build. Cargo includes protections to prevent any file from being extracted outside of the crate's own cache directory.

It was discovered that it's possible to craft a malicious tarball able to extract files one level below the crate's own cache directory. With the way the cache is structured, that allowed the malicious crate to override the cache of other crates belonging to the same registry.

Mitigations

Rust 1.96.0, to be released on May 28th, 2026, will update Cargo to reject extracting any symlink within crate tarballs, regardless of whether they come from crates.io (which already forbids them) or third-party registries. Note that Cargo never added symlinks when running cargo package or cargo publish, so the impact of this should be minimal.

Users who are not able to upgrade to the most recent Rust version are recommended to audit the contents of their registry for the presence of any symlink, and to configure their registry to reject symlink (if such option is available).

Affected versions

All versions of Cargo shipped before Rust 1.96.0 are affected.

Acknowledgements

We'd like to thank Christos Papakonstantinou for reporting this to us according to the Rust security policy.

We also want to thank the members of the Rust project who helped us address the vulnerability: Josh Triplett for developing the fix; Arlo Siemsen for reviewing the fix; Emily Albini for writing this advisory; Emily Albini, Josh Stone and Manish Goregaokar for coordinating the disclosure; Ed Page and Eric Huss for advising during the disclosure.

25 May 2026 12:00am GMT

The Rust Security Response Team was notified that Cargo incorrectly normalized the URLs of third-party registries using the sparse index protocol. If a hosting provider allowed multiple registries to be hosted with arbitrary names within the same domain, an attacker able to publish crates in a registry could obtain the credentials of others users of the same registry.

This vulnerability is tracked as CVE-2026-5222. The severity of the vulnerability is low, due to the extremely niche requirements needed to achieve the attack.

Overview

Originally Cargo only supported storing a registry's index within git repositories. Most git hosting solutions allow accessing a git repository with or without the .git suffix, so Cargo mirrored this behavior when normalizing registry URLs. This allowed credentials for https://example.com/index to be used for https://example.com/index.git.

This normalization was unintentionally applied to the new sparse indexes too. Sparse indexes can be hosted on any HTTPS server, which treat URLs ending with .git as different URLs than those without the suffix.

If the following conditions apply:

• https://example.com/index is a sparse index.
• https://example.com/index allows crates to depend on crates from any other registry.
• The attacker is able to publish crates on https://example.com/index.
• The attacker is able to upload arbitrary files to https://example.com/index.git.

...the attacker could configure https://example.com/index.git to be a Cargo sparse registry requiring authentication for downloads, and with a download URL pointing to a server recording any credentials set to it.

When the attacker then publishes a crate foo to https://example.com/index depending on a crate bar from https://example.com/index.git, and tricks the victim into downloading foo, Cargo will think the two registries share the same credential and send the victim's Cargo token to the malicious registry.

Mitigations

Rust 1.96, to be released on May 28th, 2026, will update Cargo to only strip the .git suffix from registry URLs using the git protocol. No mitigations are available for users of older versions of Cargo.

Affected versions

All versions of Cargo shipped between Rust 1.68 (the stabilization of sparse registries) and 1.96 are affected.

Acknowledgements

We'd like to thank Christos Papakonstantinou for reporting this to us according to the Rust security policy.

We also want to thank the members of the Rust project who helped us address the vulnerability: Arlo Siemens for developing the fix; Weihang Lo, Eric Huss and Emily Albini for reviewing the fix; Emily Albini for writing this advisory; Emily Albini, Josh Stone and Manish Goregaokar for coordinating the disclosure.

25 May 2026 12:00am GMT

With Jujutsu, I've been able to work in multiple workstreams more efficiently than before. This means that if I'm working on multiple things, there is a higher likelihood of something going stale while I wait for a review or touch multiple files. Dealing with conflicts aren't so bad these days, however if I can automate the easy ones, why not?

This is the prompt I've been using with my agent whenever I have a list of changes that have conflicts and don't need me to participate actively on it.

Using the jj version control system, fix the conflicts that are in the changesets from `<start_rev>` to `<end_rev>`. Keep trying until there are no more "(conflict)" in the changesets between those two IDs.

25 May 2026 12:00am GMT

24 May 2026 3:48am GMT

Leif Oines and Will Lachance introduce Glean Annotations: a process and technology for curating and communicating knowledge about the data we collect in Mozilla's products.

24 May 2026 2:56am GMT

We try to be responsible with data. For example, we: - store as little sensitive data as possible - monitor changes in incoming data on which we've built models But what happens when those two approaches conflict? How do we monitor changes in incoming data that we don't want to store? This talk explains the schema we use to monitor changes in what people are searching for in Firefox...even when we deliberately don't store some of what people are searching for.

21 May 2026 6:30pm GMT