Firefox Developer Edition 156.0b4 for Windows

Firefox Developer Edition 156.0b4 is a free version of the Mozilla Firefox browser made for web developers, available for Windows, macOS and Linux. Download Firefox Developer Edition if you build or debug websites and want the newest web platform features and developer tools before they reach the regular Firefox release.

Specifications

How it differs from regular Firefox

Firefox is released in channels. Nightly changes every day, Beta collects the features planned for the next release, and the regular Firefox gets them once they are tested. Developer Edition is built from the Beta channel, so you see new CSS, JavaScript and browser APIs several weeks early and can check whether your site breaks before visitors do. The browser also changes defaults with developers in mind: a dark theme, developer tools pinned in the toolbar, remote debugging enabled, and a separate profile. That profile matters in practice: Developer Edition can run next to your normal Firefox without sharing bookmarks, extensions or cookies, so testing does not mess up your everyday browsing. Inside the developer tools you get the inspector with CSS Grid and Flexbox overlays, a JavaScript debugger, a network monitor, performance and memory tools, an accessibility inspector and responsive design mode for checking layouts at phone sizes. Mozilla documents each release's changes for developers on MDN.

System requirements

Mozilla's system requirements list Windows 10 or later, a processor of 1 gigahertz (GHz) or faster, 1GB of RAM for the 32-bit version or 2GB of RAM for the 64-bit version, and 500MB of hard drive space. Firefox is no longer supported on Windows 8.1 and older.

How to install

1. Open the Developer Edition page on mozilla.org and choose your Windows build.
2. Run the installer; it creates its own profile and icon.
3. Sign in to a Mozilla account only if you want to sync this profile.
4. Press F12 to open the developer tools on any page.

Safety and price

Developer Edition is free and comes straight from Mozilla. It is a beta-quality build: stable enough for daily work, but occasional bugs are expected, so keep regular Firefox or another stable browser for banking and important tasks. Updates arrive often and install automatically.

Pros and cons

• Pro: new web features weeks ahead of release.
• Pro: separate profile, runs next to normal Firefox.
• Pro: strong CSS layout and accessibility tools.
• Con: beta code, occasional bugs.
• Con: frequent updates.
• Con: some extensions lag behind new versions.

Alternatives

For a stable Mozilla browser, Firefox ESR receives long-term support. Chromium-based testing is covered by Google Chrome Dev, Google Chrome Canary and Microsoft Edge, and Mozilla Firefox Portable runs without installation.