fidzu : thunderbird

We spend a lot of time browsing online. Whether you are researching for work, planning a trip, paying your bills, or scrolling through social media, your browser is there for it all.

While all these tasks are very different in nature, a lot of people still tend to stick to the same window type for all their use cases. But what if there was a different way to browse?

You may have noticed Firefox now has three window options for desktop. On top of the Classic and Private windows you've known for years, a third choice has been rolling out in beta: Smart Window. This optional AI-powered browsing experience is built to move your work forward and help finish what you started online.

Following the recent addition of several new Smart Window capabilities, we thought now would be the perfect time for a breakdown of what each of our three window options actually does, and when to use them.

Classic: Timeless and tailored to you

Classic Window is still the most customizable option of the three. While Private and Smart windows share many of the same features and capabilities as Classic, a Classic Window offers the widest range of Firefox's standard personalization options. It gives you the broadest canvas for tailoring Firefox to the way you browse.

What makes it Classic:

• Full oversight over controls, buttons, and toolbars.
• Access to the entire Firefox add-ons library.
• Advanced customization and configuration options.
• The ability to sync your history, bookmarks, and open tabs across your signed-in devices.

When to use it:

Classic is your home base. It's the best place to start customizing around your browsing needs, whether that means an extension setup specifically tailored to your workflow, a special theme that matches your style, or just the familiar Firefox experience you created over years of tweaking to your personal taste. While many customizations are also available on Private and Smart window, Classic offers the most extensive line-up of optional browser features, extensions, and aesthetics to personalize your setup.

Classic is the right move for general browsing like scrolling through social media, conducting a quick Google search, or reading online articles. It's also the best place to start if you are looking to build your browser around you.

Private Window: Browse with greater peace of mind

Private Window stays true to its name and number one priority: it's designed to limit the information associated with your browser session. When a Private Window is closed, Firefox doesn't retain session information, such as what you searched for, the sites you visited, or the cookies they set.

What makes it Private:

• Pages visited from a Private Window will not be added to the list of sites in Firefox's History menu, the Library window's history list, nor the address bar drop-down list.
• Nothing entered into text boxes on web pages and Search bar will be saved for Form autocomplete.
• Cookies set in a Private Window are kept only temporarily in memory, separate from your regular cookies, and are discarded after your last Private Window is closed.
• Extensions are off by default in a Private Window, unless you explicitly grant them permission.

When to use it:

A Private Window is recommended when you don't want activity from a browsing session sitting in your history, such as shopping for a gift. It's also helpful when browsing on a shared device, ensuring your history, logins, and cookies will not be saved for the next person.

You may not need a Private Window every time you open your browser, but it's always there for you when you do.

Smart Window: Firefox's privacy-first, AI-powered browsing experience to help get stuff done

Smart Window is Firefox's newest window type, currently rolling out in Beta to users in the U.S., Canada, and France. Think of it as a Classic Firefox window with a built-in AI assistant layered on top - one that you can choose to have utilize your open tabs, recent browsing, and the page in front of you, so it can help you do more without switching contexts - all with the privacy and security you expect from Firefox.

What makes it Smart:

• A built-in assistant that can summarize pages, generate recommendations, compare information, and plan tasks using your open tabs.
• The ability to retrieve current web information and display the sources behind its response without taking you to a separate search results page, supported by Firefox's new partnership with Exa.
• Suggested groups for related tabs and detection of duplicate tabs.
• Visual previews of pages from your browsing history, so you can surface the page you're looking for more easily among similar results without opening each one.
• The choice of three AI models to power the assistant, as well as the option to bring your own model.
• Optional "memories," built from either your Smart Window chats or your browsing activity in both Smart and Classic windows, or both. Memories help the assistant give you more helpful, personalized answers over time. They are stored locally on your device and can be deleted at any time.

When to use it:

Smart Window shines when you need a little extra help finishing what you started. Its ability to work with the context you choose to share can help you make progress on ongoing tasks that may require more than one session, like trip or event planning, comparison price shopping, or conducting research for work or personal reasons.

And with Smart Window's optional memories, which learn your patterns and preferences over time (with your permission), Smart Window gets more useful the more you use it, keeping you from having to spell everything out from scratch each time.

Selecting the right window for the job

None of these windows is "better" than the others, they're built for different moments.

The good news is you are never locked into one. Firefox lets you move between all three depending on what you're doing, so you can choose the window that fits each task.

You can access Classic and Private windows at any time from the Firefox menu. As for Smart Window, it remains in beta, with current availability to people in the U.S., Canada, and France.

To try Smart Window, visit https://www.firefox.com/smart-window. Or, if it's not available in your region yet, you can sign up to be notified when it is.

The post Classic, Private, or Smart? Choose the right Firefox window for every task appeared first on The Mozilla Blog.

24 Sep 2026 5:00pm GMT

Greetings once more from the Thunderbird development team!

As the Northern hemisphere summer comes to an end and a slew of PTO, company holidays and projects have wrapped up, what better time to share progress and next steps on the work the Thunderbird Desktop Engineering team has on their plates!?

Exchange support moving well

The powerhouse Exchange engineering team had some great momentum over the summer and completed their work on implementation of the Graph protocol to support email accounts - well in advance of their deadline. They have since moved on to start work to support Exchange calendars using the Graph protocol which is a significant milestone given that our calendar code hasn't had significant changes for some time.

While some team members are now juggling multiple projects, good progress has been made to wrestle the foundations into place, with calendar discovery and persistence in place, along with display of calendar items. Following a brief hiatus to focus on other priorities, the team is once again back into gear.

Keep track of our Graph API Calendar implementation here.

Account Setup & Authentication

Since I last wrote, many of the account setup and account authentication improvements have landed (mostly in versions 156 & 157), unlocking some important security use cases which are becoming more frequently requested and mandated by organizations and legislation around the world.

While diving into the code is an enjoyable adventure, the newly-minted articles devoted to the topic of Oauth customization might be a better starting point for most:
Knowledge Base - Custom OAuth for Thunderbird

UI overhauls - why just one?!

The front end engineering team has completed the rebuild of our account setup manual configuration flows to include new protocol options and security customizations, so it is time to pick up where we left off on our Calendar UI rebuild.

The majority of the front end team is now either focused on Calendar Event data write operations stemming from the Event Read dialog (delete event, RSVPs, Reminders) - or beginning the largest part of the journey, which is the implementation of a new Calendar Create/Edit dialog, along with REDUX-based state management, a new WYSIWYG editor and more reusable components such as date pickers.

Follow the Calendar Event Create/Edit work here

While that work is underway, why not weave in some more improvements?!

After some extensive user research and testing, our design team has begun work to improve the Settings UI, starting with some updates to humanize and homogenize the various options, headings and guidance provided in that area of the application.

Read more about that journey here

Contributions are on the rise! Some AI guidance…

In the past few months, we've seen a wonderful increase in contributions from community members - partially thanks to our move away from Mercurial to a more familiar Git-based workflow - and partially thanks to many LLMs doing a great job of interpreting our public codebase and making it far more accessible. Or it could be that our team is just such a friendly bunch that we've attracted a great group of people willing to support.

Whatever the reason, we're happy to see new names. faces and ideas in our chats and review queue!!

Having said that…We've reached the point where the velocity of work is beginning to pile up and clog our review queue - so I felt it might be time to share some guidance to make the process easier for both external contributors and the internal review team. Bear in mind that while we use AI workflows in several areas, our goal is to preserve a codebase which can be maintained by humans. We're working on a policy that may word some of these points better, but from the past few months of my experience here's what I see as being helpful:

1. Keep patches to a digestible size and understandable complexity - Contributions should save more development time than it takes to review. If the patch contribution creates heavy work for maintainers, it will be deprioritized - so the best approach is to break the work up into pieces that can be understood more easily and discussed together. Bear in mind that many cloud-based models aren't primarily designed to be frugal with token usage so it's easy for patches to grow (much) larger than they actually need to be to solve the problem. Be specific with prompts to minimize the surface area of changes so they are reviewable.
2. Humanize or write comments (within code and throughout the code review process) by hand - While we've become accustomed to interacting with a variety of automated systems in our daily lives, a good chunk of the joy involved in our work is to share knowledge with each other and refine the code so that it can be reused and understood by humans.
3. Be wary of license infringement - much of our work is under the MPL license and we must all take care not to introduce refactored code that originally came from licensed software which can be rewritten and translated using LLM, then relabelled under our licence.
4. Be transparent - it will often help to share prompts and your model when submitting code for review. Refining all aspects of our workflow is important, and we can all benefit from a collective evolution of skills and prompts that improve over time with input from the team and community.
5. We encourage contact with a member of the team to discuss approach and architecture in advance of spending time and tokens on a patch. Some areas of the codebase are already slated for redevelopment and it's not always obvious what is underway and planned. Having a quick conversation to say "Hey, I'm thinking about working on this" is a great start to landing something that spends less time in review and uses less tokens, energy & the world's natural resources.
6. Of course if none of these guidelines are followed, we'll still be very happy to receive help from the wider community - the process may just take longer and be a bit less pleasant.

Enterprise

As parts of the world turn their infrastructure priorities toward digital sovereignty, we've seen an increase in interest from governments, institutions and organizations around the world who are looking to either improve their existing FOSS-based infrastructure or deploy for the first time. That has resulted in some focused efforts throughout Q3 to improve our Enterprise security and policy framework to bring it in line with the strides that the Firefox engineering team has made, and also roll out more Thunderbird-specific administrative mechanisms that allow granular control over end user configurations. Read more about your options and follow the work below:

Thunderbird Enterprise Policies and Relevant Preferences

Thunderbird Enterprise PoC Work Items

Maintenance, Upstream adaptations, Recent Features and Fixes

Waves of changes from upstream Firefox have continually kept the team on their toes throughout July & August, but the small but mighty gang have kept Daily builds largely intact each day. In addition, the team and contributor community have continued landing a series of reliability, stability, and usability improvements across the application. Recent highlights include:

• Nico has a series of calendar improvements in the works with several now cleared for landing: D319397, D320418, D320419
• Hurtmut has again come to the rescue with a number of patches but most recently solved a widespread filtering problem introduced upstream which will need to be uplifted as a matter of urgency.
• Richard pushed many patches since my last update, many related to upstream changes required after the Firefox project "Nova" was unleashed. He's also been on the lookout for other breaking changes such as XUL attribute modifications.
• Max was on fire and in constant comms with the team to deliver a large number of important changes but also helped to refine some of our processes relating to AI-driven workflows. Recently, he led an investigation into growing concerns over instability with connections with Gmail accounts in Bug 2028760.
• and many more which are listed in release notes for beta.

If you would like to see new features as they land, and help us find some early bugs, you can try running daily and check the pushlog to see what has recently landed. This assistance is immensely helpful for catching problems early.

-

Toby Pilling

Senior Manager, Desktop Engineering

The post Thunderbird Monthly Development Digest: September 2026 appeared first on The Thunderbird Blog.

23 Sep 2026 10:35pm GMT

Bugs resolved in Moz-Phab 2.20.0:

• bug 2066178 Drop support for Python 3.9
• bug 2068605 preserve file logging from moz-phab list --format json and moz-phab patch --raw
• bug 2071586 Review queue reminders should ignore group reviews (at least optionally)
• bug 2073088 moz-phab submit is getting the file size from hg/git even if it could infer it from the blob itself
• bug 2074036 List index out of range

Discuss these changes in #engineering-workflow on Slack or #Conduit Matrix.

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23 Sep 2026 4:45pm GMT