Firefox Nightly 90.0a1 (2021-04-29) has a new “Nightly Experiments” section in the “Settings” page.
⬜ about:home startup cache
A cache for the initial about:home document that is loaded by default at startup. The purpose of the cache is to improve startup performance.
⬜ Address Bar: show results during IME composition
An IME (Input Method Editor) is a tool that allows you to enter complex symbols, such as those used in East Asian or Indic written languages, using a standard keyboard. Enabling this experiment will keep the address bar panel open, showing search results and suggestions, while using IME to input text. Note that the IME might display a panel that covers the address bar results, therefore this preference is only suggested for IME not using this type of panel.
⬜ Cookies: SameSite=Lax by default
Treat cookies as “SameSite=Lax” by default if no “SameSite” attribute is specified. Developers must opt-in to the current status quo of unrestricted use by explicitly asserting “SameSite=None”.
⬜ Cookies: SameSite=None requires secure attribute
Cookies with “SameSite=None” attribute require the secure attribute. This feature requires “Cookies: SameSite=Lax by default”.
⬜ Cookies: Schemeful SameSite
Treat cookies from the same domain, but with different schemes (e.g. http://example.com and https://example.com) as cross-site instead of same-site. Improves security, but potentially introduces breakage.
⬜ CSS: Constructable Stylesheets
The addition of a constructor to the CSSStyleSheet interface as well as a variety of related changes makes it possible to directly create new stylesheets without having to add the sheet to the HTML. This makes it much easier to create reusable stylesheets for use with Shadow DOM. See bug 1520690 for more details.
⬜ CSS: Masonry Layout
Enables support for the experimental CSS Masonry Layout feature. See the explainer for a high level description of the feature. To provide feedback, please comment in this GitHub issue or this bug.
⬜ Developer Tools: Color Scheme Simulation
Adds an option to simulate different color schemes allowing you to test @prefers-color-scheme media queries. Using this media query lets your stylesheet respond to whether the user prefers a light or dark user interface. This feature lets you test your code without having to change settings in your browser (or operating system, if the browser follows a system-wide color scheme setting). See bug 1550804 and bug 1137699 for more details.
⬜ Developer Tools: Compatibility Panel
A side panel for the Page Inspector that shows you information detailing your app’s cross-browser compatibility status. See bug 1584464 for more details.
⬜ Developer Tools: Execution Context Selector
This feature displays a button on the console’s command line that lets you change the context in which the expression you enter will be executed. See bug 1605154 and bug 1605153 for more details.
⬜ Developer Tools: Service Worker debugging
Enables experimental support for Service Workers in the Debugger panel. This feature may slow the Developer Tools down and increase memory consumption.
⬜ Fission (Site Isolation)
Fission (site isolation) is an experimental feature in Nightly to provide an additional layer of defense against security bugs. By isolating each site into a separate process, Fission makes it harder for malicious websites to get access to information from other pages you are visiting. This is a major architectural change in Nightly and we appreciate you testing and reporting any issues you might encounter. For more details, see the wiki.
⬜ HTTP/3 protocol
Experimental support for the HTTP/3 protocol.
⬜ Media: AVIF
With this feature enabled, Nightly supports the AV1 Image File (AVIF) format. This is a still image file format that leverages the capabilities of the AV1 video compression algorithms to reduce image size. See bug 1443863 for more details.
⬜ Multiple Picture-in-Picture Support
Experimental support for allowing multiple Picture-in-Picture windows to be open at the same time.
⬜ Web API: inputmode
Our implementation of the inputmode global attribute has been updated as per the WHATWG specification, but we still need to make other changes too, like making it available on contenteditable content. See bug 1205133 for more details.
⬜ Web API: WebGPU
This new API provides low-level support for performing computation and graphics rendering using the Graphics Processing Unit (GPU) of the user’s device or computer. The specification is still a work-in-progress. See bug 1602129 for more details.
⬜ WebRTC Global Mute Toggles
Add controls to the WebRTC global sharing indicator that allow users to globally mute their microphone and camera feeds.
⬜ Win32k Lockdown
Disable use of Win32k APIs in browser tabs. Provides an increase in security but may currently be unstable or glitchy. (Windows only)
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Users of the Nightly build can now easily enable/disable experimental features in the Nightly build in the “Nightly Experiments” section.