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Launching Web Serial in Firefox 151

The web is built by communities, but not all communities use the web the same way.

That philosophy shaped part of this week's Firefox 151 release, which introduced support for the Web Serial API on desktop. Most folks won't use this API, but for our community of builders and tinkerers, it unlocks the ability to use Firefox to communicate directly with compatible hardware devices like microcontrollers, development boards, and other serial-connected devices.

For developers, makers, educators, hardware enthusiasts, and embedded-device communities, browser-based hardware workflows have increasingly become part of the modern web experience. With Firefox's browser engine, Gecko, now supporting Web Serial, users can now connect, code, configure, and control compatible hardware directly from the browser in many workflows, often without additional software or complicated setup.

If you want to dive deeper into the technical details behind Web Serial support in Firefox 151, you can read our full engineering post here.

Adafruit collaboration

As part of this week's launch, Adafruit, one of the internet's most beloved open-source hardware communities, is collaborating with us to test and validate what browser-based hardware development can look like in Firefox with Web Serial support.

If you've ever spent time with CircuitPython, browser-based board programming, custom controllers, sensors, classroom kits, STEM homework assignments, or a desk covered in blinking microcontrollers-you probably already know Adafruit.

With Web Serial support in Firefox 151, Adafruit's browser-based hardware workflows now work directly in Firefox as well, with no additional software or complicated setup required for many projects. We invite you to give it a try.

Different communities care about different browser experiences. Some people want simplicity, familiarity and productivity. Others want flexibility, customization, and tools that support the way they work, build, experiment, and create. We want the web to be open, flexible, and shaped by the diversity of people building on it.

If you're wiring up your first board, experimenting with hardware projects, or dusting off an old electronics kit, give Adafruit and Web Serial in Firefox a try.

Build something amazing. Make something useful. Tell us what works. Tell us what breaks. Most of all, make it your own.

The post Mozilla and Adafruit bring Web Serial workflows to Firefox appeared first on The Mozilla Blog.

21 May 2026 6:00pm GMT

Support for Web Serial in Firefox 151 for Desktop

Firefox can now connect directly to microcontrollers, development boards, 3D printers, power meters, and other serial-connected hardware from the web. Starting in Firefox 151 for Desktop, support for the Web Serial API allows web applications to communicate with compatible devices without requiring native software.

Web Serial compatible devices are popular among hobbyists, hardware hackers, educators, makers, and developers with use cases ranging from home automation to hardware prototyping and 3D printing. Web Serial support makes Firefox more useful for these kinds of projects.

Here's an example using an Adafruit ESP32-S2 based board where messages sent from web code can be directly displayed on the device over Web Serial.

We've collaborated with Adafruit to test Firefox's implementation against real hardware workflows commonly used by this community. The result: Firefox is a more practical browser for programming and interacting with hardware directly using web technology.

As an example of how you can combine Web Serial with electronics, Mozilla engineer Alex Franchuk created an amazingly fun and functional device that melds electronics and web editing. Check out the Page Playground.

The list of serial compatible devices includes Espressif ESP-based boards such as the popular ESP32 chips, Raspberry Pi Picos, 3D printers, LEGO devices, and many more. There are many tools for running your own code on these small affordable microcontroller boards, and with Web Serial it's easier than ever to connect them to a computer and interact through a web-based user interface.

What is Web Serial?

Web Serial is a web API that allows a website to read and write to serial devices using JavaScript. See the MDN documentation for the details. While modern computers don't typically include serial ports, serial devices connected to a USB port or paired via Bluetooth can advertise themselves as serial-capable devices so they appear as serial ports in the operating system.

The Web Serial API lets developers use the web platform to communicate with these devices. For example, websites can control devices or deliver firmware without requiring native applications or installers.

Mozilla's own Florian Quèze, who has experimented with many projects to measure power consumption, demonstrated how Web Serial could be used to read power data from an off-the-shelf USB power meter and display it in Firefox. Florian's code can also export the data into the Firefox Profiler, making it easy to visualize and share power data. Here's the page and GitHub repo. The screenshots below show the page in action and the data in the Firefox Profiler after recording the power usage of a light with three brightness modes.

Home Assistant is another example. It's a popular (and growing) open source project for home automation. The ESPHome project offers Home Assistant-compatible firmware for affordable ESP32 and similar devices which can be installed and configured over Web Serial in just a few clicks.

Security and Privacy

There are clear security and privacy concerns with allowing the web platform to read and write to hardware devices. Most importantly, with Web Serial, websites do not have visibility or access to serial ports until the user explicitly allows it.

Ports are allowed on a per-site and per-port basis. The Web Serial API requires websites to call navigator.serial.requestPort(), which lets the user choose which port to allow access to, or disallow all access entirely. This means websites do not receive a list of connected devices and there is no useful fingerprinting information outside of the port the user selects.

To help users understand when and why a site requests access to a serial port, Firefox uses add-on gating which we introduced with our Web MIDI API implementation. Compared to other web permission prompts, this gives the user a more detailed explanation of what they're allowing. The add-on gating prompts appear before the port selection prompt the first time a site requests port access.

For organizations using Firefox Enterprise Policies, Web Serial is disabled by default. Administrators can explicitly allow or disallow Web Serial functionality across their organization using the DefaultSerialGuardSetting policy setting.

Standardization

While Web Serial still resides in the Web Incubator Community Group (WICG), we're optimistic there's a path to standardization given its scope and long-running incubation. We are pursuing standardizing the Web Serial API in the WHATWG in a new Workstream proposal and are excited to work with ecosystem partners and standards bodies to help shape access to peripherals on the web.

Feedback

If you already have a Web Serial workflow with a device you can test on, give Firefox a try. We'd love to hear what you're building and which workflows matter most to you. Mozilla Connect is a great place to share projects, ask questions, and give feedback.

For technical issues, browse to support.mozilla.org or file a bug here.

The post Announcing Web Serial Support in Firefox appeared first on Mozilla Hacks - the Web developer blog.

21 May 2026 6:00pm GMT

Crafted with care. Built for speed. Ready for what's next.

A great browser is so intuitive that you often forget you're using it. Yet today the internet is changing faster than ever, and your browser needs to keep up. Firefox is still the only browser built for people, not platforms: independent, customizable, private and firmly in users' control.

Keeping Firefox the best browser for being online today is what motivated our recent work to update Firefox's design and design system. We're aiming to deliver a more cohesive foundation for Firefox: making the browser feel cleaner, warmer, faster and more adaptable.

Internally, we've been calling this work Project Nova. The name fits: A nova can look like a new star, yet it comes from existing matter - a renewal, not a replacement. When it rolls out later this year, you can just call it Firefox. Here's what it's all about:

Privacy at the center

A good default matters. When you choose Firefox, privacy and clear data practices are there from the start. Our new design pulls privacy features forward, making it easier to find and use tools like our free, built-in VPN and private browsing.

We're also redesigning Settings so choices about your data are easier to understand and act on. That includes controls for turning off AI features entirely, plainer language throughout, as well as tuning Enhanced Tracking Protection to match your preferred balance of protection and usability.

Speed you can feel

Privacy and speed aren't trade-offs. When Firefox blocks trackers, pages load faster, too. We also prioritize the most important parts of a page before the optional stuff around the edges. In the last year, we've improved load times for key page content by 9%.

The new design can speed up your workflows, too. It's easier to access tab groups, split view, and vertical tabs - putting these productivity features at your fingertips, but not in your face.

And we're bringing back compact mode. People told us that they missed it, and we listened. If you want your browser controls as condensed as possible, this one's for you.

Balancing the new and familiar

When it came to design, we wanted Firefox to feel current, but not generic. Warm, but still precise. More expressive, but never louder than the web itself. You'll see the change first in the fundamentals:

• Tabs have a softer shape, with a subtle gradient that gives the active tab more presence and creates a sense of light around the browser chrome.
• Components are more rounded and consistent, so panels, menus, settings and browser controls feel like part of the same system.
• Icons have been updated to feel cleaner and more balanced across light and dark themes, supporting quick recognition without adding visual noise.
• Spacing is rebalanced across the interface with the knowledge that every pixel matters when the browser is where you spend your day.
• The refreshed color palette is inspired by the feeling of fire: the glow around your active tab, deep smoky purples and lighter tones that add warmth.

The voice is warming up, too. Firefox copy is becoming more direct, more human, and sometimes more playful or fiery. Always genuine… because that's what sets Firefox apart.

The effect is distinctly Firefox: approachable and energetic, while still easy to scan. Under the hood, reusable tokens, components, patterns, and a shared design language make Firefox easier to evolve over time, so new features feel integrated instead of bolted on.

The redesign is most visible on desktop, but the work extends to mobile, too. Shared colors, icons, copy and design foundations help Firefox feel more consistent across devices.

Yours to shape

Firefox has long been the most customizable browser. It's in our open source DNA. Now we're adding more ways to make Firefox feel like yours, including new themes and wallpapers. And we're exploring more customization over time, like controls for the shape of the interface - tabs, components, and related visual treatments.

Accessibility is a key part of customization. Firefox is being designed with attention to contrast, readability, focus states, keyboard behavior, target sizes, system settings, visual comfort, and how the interface works across themes and windows.

Dark mode, for example, is not just a preference for many people. It is their default environment. For some, it helps reduce eye strain. For others, it is part of a broader system setup.

Building in public

Firefox has always been built in the open, and with the help of a global community of contributors and supporters. You help us build the browser, test, extend and improve it. You tell us when something doesn't feel right. That relationship is part of what makes Firefox different.

While the new design system for Firefox is still being shaped, keep telling us what feels right, and what gets in your way. We're listening.

The post Designing Firefox for the future appeared first on The Mozilla Blog.

21 May 2026 12:55pm GMT