Mozilla Firefox Developer Edition

Firefox Developer Edition is Mozilla's browser distribution for web development, combining browser features with tools for inspecting and debugging websites. It suits developers who want to test web content and explore upcoming browser behavior in a separate development-focused installation.

Features

• Inspect HTML and CSS with the browser's developer tools.
• Debug JavaScript and examine web console output.
• Inspect network activity and supported performance diagnostics.
• Test supported responsive layouts and device-sized viewports.
• Use a development release channel for earlier access to browser changes.

Setup and compatibility

The official 158 beta requirements list macOS 10.15 or later, an Intel or Apple Silicon processor, 512MB RAM and 200MB disk space. Allow additional space for profiles, caches and downloads. This catalog download is the en-US 158.0b5 Mac build. Install the official distribution and choose whether to use it as your default browser; keep development experiments separate from important browsing sessions where practical.

Firefox is free and open source. Its source is offered under several open-source licenses, including Mozilla Public License 2.0; Mozilla grants a personal, non-exclusive license to use the official executable distribution. Redistribution must follow the applicable component licenses and Mozilla trademark rules. Official Firefox terms and MPL 2.0. Developer Edition uses prerelease browser code, so features can change and extensions or sites may behave differently from the stable release. Review privacy, synchronization and usage-data settings before linking an account or browsing sensitive material. Developer tools can display credentials and request data from the page you are testing; handle captured network logs accordingly. Websites and extensions have their own data practices.

Sources: Official Developer Edition page, Official158 beta requirements.