Download Firefox Developer Edition 127.0

New
- You can now set Firefox to automatically launch whenever you start or restart your Windows computer. Setting Firefox to auto-launch optimizes efficiency in our browser-centric digital routines, eliminating manual startup delays and facilitating immediate web access. (Learn more)
- In Firefox 127, we completed work to optimize and enable DNS prefetching for HTTPS documents via the rel="dns-prefetch" link hint. This standard allows web developers to specify domain names for important assets that should be resolved preemptively.
- It is now possible to close all duplicate tabs in a window with the Close duplicate tabs command available from the List all tabs widget in the tab bar or a tab context menu.
Changed
- To reduce user fingerprinting information and the risk of some website compatibility issues, report 32-bit x86 Linux's CPU architecture as x86_64 in Firefox's User-Agent string and navigator.platform and navigator.oscpu Web APIs.
- Links and other focusable elements are now tab-navigable by default on macOS, instead of following macOS' "Keyboard navigation" setting. This is a more accessible default and matches the default in all other platforms. A checkbox in the settings page still allows users to restore the old behavior.
- We've updated the screenshots feature in Firefox. You can now take screenshots of various :about: pages within Firefox. Plus, you can now screenshot file types like SVG, XML, and more. We've also implemented new keyboard shortcuts and keyboard accessibility, making the screenshot tool more accessible to everyone. Additionally, we've introduced theme compatibility and High Contrast Mode (HCM) support. And not to forget, we've improved performance for capturing large screenshots.
Developer

Web Platform
- navigator.clipboard.read()/write() has been enabled (see documentation). A paste context menu will appear for the user to confirm when attempting to read clipboard content that is not originated from a same-origin page.
- Added support for the new Set JavaScript methods for creating unions and intersections of two sets.