Popular: Data updated October 27, 2026

Categories

Internet1,356
Communication321
Audio & video898
Graphics & design539
Office & productivity1,124
Developer tools3,134
AI tools529
Security & privacy385
System tools3,114
Games523
Education & science239
Network & IT284

Firefox Developer Edition (eo) 138.0 download

Firefox Browser Developer Edition

This is an older version. The current version is 151.0. Firefox Developer Edition (eo) 151.0 · Released:

Installer files 138.0

ArchitectureTypeScopeFile sizeDownloadSHA256
64-bit EXE (NSIS) All users — download-installer.cdn.mozilla.net VirusTotal
ARM64 EXE (NSIS) All users — download-installer.cdn.mozilla.net VirusTotal
32-bit EXE (NSIS) All users — download-installer.cdn.mozilla.net VirusTotal

Link and SHA256 come from the Windows Package Manager community manifest. Compare the hash of the downloaded file before running it.

Release notes

New
- Firefox for Android now supports TLS client authentication certificates. When a TLS server requests authentication from the browser, Firefox can now make use of the client certificates that have been added to your Android device.
- Desktop mode in Firefox for Android is now enabled by default on tablets, but can still be disabled from the Site Settings.
- You can now copy links for background tabs using the tabstrip context menu on MacOS and Linux.
- Firefox on Windows 11 now uses acrylic-style menus for popup windows, which better match the operating system’s aesthetic. Users who wish to customize this behavior can do so via the widget.windows.mica.popups preference.
- Firefox for Android now allows you to share a downloaded file or its original URL from the Downloads screen.
Changed
- Rededicated previous color settings to Contrast Control settings. (Learn more)
- Improved the address and credit card autofill experience to better handle forms that update dynamically as users input information. Autofill now correctly fills newly revealed fields—such as those shown after selecting a country.
Developer
- Added support for the error.captureStackTrace extension to avoid incompatibility with other browsers. (Learn more)
- We have implemented support for Error.isError, which allows for brand checking whether or not an object is an instance of Error. (Learn more)
- Firefox 138 beta users will have the change where <h1> always has the same UA style, even in <article>, <aside>, <nav>, and <section>. (Learn more)
This feature is part of a progressive roll out.
What is a progressive roll out?
Certain new Firefox features are released gradually. This means some users will see the feature before everyone does. This approach helps to get early feedback to catch bugs and improve behavior quickly, meaning more Firefox users overall have a better experience.
- Added support for the import map integrity field. You can now ensure the integrity of dynamically or statically imported modules.
- A new column was added to the Network panel showing the full path of the request URL. This enhancement makes it easier for developers to quickly view and analyze the complete request paths.
Web Platform
- Applications can now set their preferred degradation method to be utilized when encoding the configured frame rate and resolution cannot be maintained. (Learn more)
- Introduced support for Import Attributes, allowing developers to specify additional metadata when importing modules.
- Firefox now enables the cache directive for the Clear-Site-Data header, allowing websites to clear the networking cache. The header gives websites more control over data stored for their users, such as clearing the network cache during logout, mitigating the risk of privacy leaks. (Learn more)

https://www.mozilla.org/firefox/138.0beta/releasenotes/

Most popular in Web browsers

See all
  1. BraveSecure, Fast & Private Web Browser with Adblocker
  2. WaterfoxFast and Private Web Browser
  3. qutebrowserA keyboard-focused browser with a minimal GUI.
  4. geckodriverWebDriver for Firefox
  5. SafariThe Windows version (Last updated in 2012) of Apple's web browser.
  6. Microsoft EdgeMicrosoft Edge is a cross-platform web browser built for modern life.
  7. ungoogled-chromiumGoogle Chromium without dependency on Google web services.
  8. Google ChromeThe Fast & Secure Web Browser Built to be Yours
  9. Ablaze FloorpFloorp is built on Firefox and was built in Japan and is a new browser with excellent privacy & flexibility.
  10. LibreWolfA custom version of Firefox, focused on privacy, security and freedom.

More from Mozilla

See all
  • geckodriverWebDriver for Firefox
  • sccacheSccache is a ccache-like tool. It is used as a compiler wrapper and avoids compilation when possible. Sccache has the capability to utilize caching in remote storage environments, including various cloud storage options, or alternatively, in local storage.
  • Mozilla Thunderbird (en-US)Thunderbird is a free email application that is easy to set up and customize - and it's loaded with great features!
  • Dot BrowserDot Browser is a privacy-conscious web browser based on Firefox
  • mozregressionAn interactive regression rangefinder for quickly tracking down the source of bugs in Mozilla nightly and integration builds.
  • Ghostery Private BrowserThe Ghostery Desktop Browser is a minimal fork of Firefox optimised for privacy.

Tags

Share