Mozilla shipped Firefox 143 to the stable channel this week, bringing two long-awaited capabilities to the open-source browser: a Microsoft Copilot option inside its AI sidebar, and a Labs experiment that lets Windows users pin any website to the taskbar as a simplified app. The update also tightens fingerprinting protections, adds a private-browsing download scrubber, and rolls out xHE-AAC audio support on modern platforms, making this more than a routine maintenance release.

What actually shipped in Firefox 143

Copilot lands in the AI sidebar

Firefox’s AI sidebar has acted as a provider-agnostic container for web-based assistants since Mozilla first rolled it out as an opt-in feature. With version 143, Microsoft Copilot joins the list of selectable services, sitting alongside ChatGPT, Gemini, Claude, and Le Chat Mistral. The integration is strictly a web-UI convenience: selecting Copilot opens the familiar chat interface inside the sidebar panel, but the model execution, data processing, and account management all happen on Microsoft’s servers under Microsoft’s own privacy terms.

The practical upshot is that what you see is the standard Copilot web experience, complete with sign-in prompts for full functionality. Anonymous use is possible but typically triggers a verification challenge and may limit feature access. Mozilla does not bake any local AI inference into this release—the sidebar merely frames the remote assistant so you don’t have to open a separate tab. Early previews have suggested that the sidebar can expose conversation modes like “Think Deeper” or route queries to advanced backends, but those are server-side behaviors controlled by Microsoft and not guaranteed. As of this writing, official Microsoft documentation hasn’t confirmed the backend routing details, so treat those claims as provisional.

Windows web apps go live in Firefox Labs

For years, Windows users who wanted progressive web apps in Firefox had to lean on third-party tools or switch browsers. Firefox 143 introduces a native—though still experimental—pinned-sites workflow under Firefox Labs. Once enabled, visiting a site and clicking the new address-bar icon pins a shortcut to the Windows taskbar that launches the site in a simplified window. The resulting window is more like a chromeless Firefox tab than a true PWA: it retains an address bar, back/forward buttons, the extensions menu, and the hamburger menu, and your installed add-ons continue to work inside it.

Think of it as a dedicated, distraction-light web app container that keeps your extensions and browsing context intact. That’s a deliberate design choice—Mozilla chose to preserve extension functionality rather than strip everything down to a bare sandbox, which is what many Chromium-based PWA implementations do. The trade-off is that you don’t get the full, standalone PWA experience (background service workers, push notifications, install hooks) that users of Edge or Chrome might expect.

The feature is Windows-only for now, with Mac and Linux support on the roadmap. Notably, MSIX/Store builds of Firefox are excluded from this preview, so users who installed Firefox through the Microsoft Store won’t see the option yet. Early testers have reported occasional icon duplication or taskbar glitches, so treat it as a Labs experiment and test cautiously before deploying it widely.

Privacy, security, and media refinements

Alongside the headliners, Firefox 143 brings several smaller but meaningful improvements:

  • Fingerprinting resistance: Additional system attributes are now normalized to reduce browser fingerprint entropy, an incremental defense that makes it harder for trackers to uniquely identify you.
  • Private browsing download auto-delete: When you download a file in Private Browsing mode, Firefox will now offer to delete that file automatically when the private session ends. The preference is off by default but can be toggled in settings.
  • Camera permission preview: The permission prompt now shows a live camera feed, helping you select the correct webcam before granting access.
  • xHE-AAC audio playback: Firefox now supports the xHE-AAC codec on Windows 11 version 22H2 and later, macOS, and Android 9+, improving low-bitrate audio compatibility for streaming services.
  • Accessibility upgrades: Improved Windows UI Automation bindings make Firefox work better with assistive technologies like Narrator and Voice Access.

What it means for you

For everyday users

If you’re a Windows user who relies on Copilot for quick answers, switching to Firefox no longer means giving up that convenience. You can pin the sidebar open and chat with Copilot without launching Edge or a dedicated app. Similarly, the web app feature lets you turn frequently used sites—email, calendars, project boards—into taskbar icons that feel more like desktop programs, reducing tab clutter.

The caveat is that both additions are opt-in. The AI sidebar must be enabled in Settings under Firefox Labs, and web apps require flipping the “Add sites to your taskbar” checkbox. Out of the box, Firefox 143 behaves like any other Firefox release; it won’t force AI or pinned sites on anyone.

For power users

Power users who live inside Firefox will appreciate two design decisions: the ability to switch AI providers on the fly, and extension compatibility inside web app windows. Because the sidebar supports multiple assistants, you aren’t locked into Copilot; you can pick whichever bot fits your workflow or privacy tolerance. And because the pinned-site windows retain your installed add-ons, a password manager, ad blocker, or dark-reader extension will still function inside that “app” window—something many Chromium PWAs don’t allow.

On the flip side, if you were hoping for Chromium-parity PWAs with background sync and offline capabilities, Firefox’s implementation will feel like a step back. It’s essentially a taskbar launcher for a dedicated tab, not a full offline-first app container. Power users who depend on PWA-only features like push notifications should keep using Edge or Chrome for those specific sites until Mozilla decides to expand the feature set.

For privacy-conscious users

Mozilla’s privacy-first posture remains intact. The AI sidebar is disabled by default, and administrators can suppress it entirely via about:config or policy. The fingerprinting enhancements and private-download cleaning are genuinely useful for anyone who wants to minimize their digital footprint. However, the mere presence of cloud-based AI assistants inside the browser creates a new awareness burden: using Copilot, ChatGPT, or Gemini in the sidebar transmits your prompts and uploads to the respective providers. That’s no different from using those services in a regular tab, but the frictionless sidebar access might lull some users into a false sense of local processing. If you handle sensitive data, treat any AI chat in the sidebar as an external cloud service.

For IT administrators

Copilot in Firefox breaks Microsoft’s Edge-exclusive convenience, but it also opens a compliance can of worms. Employees can now access enterprise Copilot features from a non-managed browser, potentially pasting sensitive documents, code, or customer data into a cloud chat interface without oversight. Security teams should update acceptable-use and data-handling policies to explicitly cover third-party AI assistants accessed through any browser, not just Edge. Managed deployments can block the AI sidebar completely by locking the relevant browser.ml.* preferences or by disabling Firefox Labs features via Group Policy or MDM.

The web apps feature is less risky but still worth testing before wide rollout. Since MSIX/Store installs are excluded, organizations that deploy Firefox through the Microsoft Store won’t see the option; MSI-based deployments will. Validate the packaging channel you use and pilot the feature on a handful of machines to catch any taskbar or icon duplication issues before employees start complaining.

How we got here

Firefox’s AI sidebar first appeared as an opt-in Labs experiment in early 2024, initially with just a couple of providers. Mozilla’s strategy was clear: build a provider-agnostic chat surface that keeps the browser nimble and respects user choice, rather than baking in a single, heavy AI model. Since then, the list of supported assistants has grown steadily, reflecting the competitive AI landscape where users increasingly expect seamless access to their preferred chatbot.

The Windows web app feature has been on community wishlists for years. Firefox once supported a full PWA implementation under the name “Progressive Web Apps,” but Mozilla pulled the plug in 2021, citing maintenance burden and low usage—a decision that frustrated Windows users who saw Edge and Chrome offer desktop-like site experiences. Since then, community efforts like the “PWAsForFirefox” project filled the gap, but native support remained absent. Firefox 143’s pinned-sites feature is Mozilla’s first concrete step back into this territory, albeit with a deliberately lightweight approach that prioritizes extension compatibility over full PWA parity.

The timing is strategic. Microsoft has been aggressively promoting Copilot inside Edge, creating a feature gap that might tempt Firefox users to switch browsers for AI convenience. By opening the AI sidebar to Copilot, Mozilla removes that lock-in lever while still offering alternative providers. Simultaneously, the web app feature—though limited—signals that Mozilla is listening to the long-standing demand for better Windows integration.

What to do now

Try Copilot in the sidebar

  • Open the sidebar (View → Sidebar or the sidebar icon). If the AI chatbot isn’t visible, go to Settings → Firefox Labs and enable “AI Chatbot.”
  • Select Copilot from the provider dropdown. Sign in with a Microsoft account for full access, or proceed anonymously (expect a CAPTCHA).
  • To disable the AI sidebar entirely: in Firefox Labs, turn off the AI Chatbot toggle. Advanced users can set browser.ml.chat.enabled to false in about:config.

Enable web apps on Windows

  • Navigate to about:preferences#experimental and check “Add sites to your taskbar.” Restart Firefox.
  • Visit any website, click the new app icon in the address bar (a square with a downward arrow), and confirm to pin.
  • To unpin, right-click the taskbar icon and remove it, or manage it like any other shortcut.
  • If you experience icon duplication or instability, disable the experiment in Labs and report the issue to Mozilla.

Lock down for privacy or enterprise

  • Home users who want no AI footprint: disable the AI chatbot in Labs and verify that browser.ml.chat.enabled is false. Use Private Browsing and turn on the “Delete downloads after session” prompt for ephemeral files.
  • IT admins: push enterprise policies to disable browser.ml.chat.enabled, browser.ml.chat.sidebar, and browser.ml.enable. Block or allow specific providers through network egress controls if needed. Test the web app feature on your installation packaging (MSI vs. MSIX) before deploying Firefox 143 broadly.

Outlook

Firefox 143 is a pragmatic release that narrows two feature gaps without compromising Mozilla’s user-choice principles. The AI sidebar will likely see more provider options and perhaps deeper integration—expect Mozilla to explore local, on-device models as they mature and as privacy demands grow. The web app experiment is clearly a work in progress; if community feedback is positive and the icon duplication gremlins are squashed, we could see a more polished version land on the stable track, possibly expanding to Mac and Linux. For now, this release corrects a long-standing frustration for Windows users and gives AI-curious Firefox loyalists a reason to stay put. Watch for Mozilla’s next moves on both fronts—they’ll signal whether Firefox intends to compete head-on with Chromium’s app ecosystems or carve out a unique, extension-friendly middle ground.