Mozilla Firefox Developer Edition158.0b3

Mozilla Firefox Developer Edition lets you browse the web on a Mac while providing tools for building, inspecting, testing, and refining sites. Mozilla’s official browser edition is aimed at developers and people evaluating a development-focused version of Firefox, and belongs to the Internet & Browsers category.

It combines fast browsing with beta-stage developer tools, including a Multi-line Console Editor and WebSocket Inspector. A separate profile and application path allow it to run alongside Firefox Release or Beta without sharing their setup. Browser and remote debugging are enabled by default, while a dark theme and developer-toolbar button are included in its developer-oriented preferences.

Firefox DevTools can visualize CSS Grid layouts, display associated area names, preview transformations, and help refine grid-based designs. It grays out ineffective CSS declarations and explains why they are not applied, sometimes suggesting a fix. The fonts panel reports an element’s font source, weight, style, and related details, while the wider toolkit supports code inspection, network monitoring, emulated-device testing, animation and spacing adjustments, memory-leak investigation, and in-browser CSS stylesheet management.

macOS 10.14 and earlier are no longer supported, and the Mac build supports both Intel and Apple Silicon processors. The current version is 158.0b3, and the software is available under a freeware license. Firefox Developer Edition automatically sends feedback to Mozilla during use.