Firefox Nightly 153.0a1

Starting with Firefox 152, Nightly builds have an in-memory cache for the JavaScript compilation result, which is shared across navigation within the same domain, in order to improve the page load performance. The cache works in the same way as the existing in-memory cache for the stylesheets and the images. This can affect how the cached requests/responses are handled in DevTools, WebDriver, and WebExtensions APIs such as webRequest and decla…

Starting with Firefox 151, Firefox for Android nightly builds include settings for enabling fine-grained control of AI features and also allows you to block future AI features.

Starting with Firefox 152, the address bar in Nightly builds autofills the pages you visit most - including specific pages within a site, not just site homepages - based on your browsing habits, and lets you dismiss suggestions you don’t want.

Added support for Apple's system-wide full-screen keyboard command (Globe-F)

Share any open page with a QR code. Right-click a tab, select Share > Generate QR Code. Great for posters, invitations, banners, and other printed materials. On macOS, you can also right-click the address bar to access the Share menu.

Firefox Labs can now be opened quickly by typing "labs" or "experiment" in the address bar and selecting the Open Firefox Labs quick action.

In Firefox for Android , sharing a remote PDF will now share the file itself, rather than its URL, that you can still share by copying it from the awesomebar.

Firefox Settings features a brand-new look with streamlined organization, clearer groupings, and improved navigation for easier customization.

Text selected in PDFs is now highlighted clearly like in normal web pages. The selection color also follows OS settings like high-contrast mode.

Developer Information

Starting with Firefox 151, the JavaScript Tracer can be enabled from DevTools Settings panel in Nightly builds. This enables tracing all JavaScript function calls. Unlike the performance profiler, this doesn't record a sample; instead, it traces all function calls.

Starting with Firefox 152, Nightly builds now support the WebAssembly JS-Promise-Integration proposal, improving the porting of applications to the Web.

Starting with Firefox 152, Nightly builds allow the attr() function to be used in any CSS property. It now also allows to specify how the attribute value is parsed into a CSS value.

Updated HTML parsing rules for <select> elements, aligning with web standards to support future customizable select dropdown features.

The vertical-align property was converted into a shorthand for baseline-source , alignment-baseline , and baseline-shift in Firefox 149. Now, alignment-baseline supports the new keywords alphabetic , ideographic , central , mathematical , and hanging , extending the variety of baselines to choose for alignment .

Implemented the new popover=hint spec, which removes a series of inconsistent and unexpected behaviors.

Starting with Firefox 153, Nightly builds support the new JPEG XL image format , which generally has better compression than WebP, JPEG, PNG and GIF and is designed to supersede them.

The circle() and ellipse() functions accept two new keywords closest-corner and farthest-corner for their radial size.

The newly added Error.stackTraceLimit property allows to set the maximal depth of the captured JavaScript error stack as a performance optimization.

Developers can now use the text import attribute to import text files using the module system.