Mozilla Firefox Developer Edition

About

Firefox Developer Edition is a browser built for developers working on the open web. It includes the latest developer tools in beta, along with features such as the Multi-line Console Editor and WebSocket Inspector. It runs with its own separate profile and path, so it can sit alongside the Release or Beta versions of Firefox.

The browser comes with preferences tailored for web developers: browser and remote debugging are enabled by default, as are the dark theme and a developer toolbar button. Its DevTools include an Inactive CSS feature that grays out declarations with no effect on the page and explains why, a fonts panel showing font source, weight, and style, and tools for working with CSS Grid, such as visualizing the grid and previewing transformations. Other panels cover inspection, the console, a JavaScript debugger, network monitoring, storage, responsive design mode, visual editing, performance, memory, and a style editor.

Firefox Developer Edition is available for macOS, among other platforms. The page notes it is no longer supported on macOS 10.14 and below, in which case Firefox ESR is recommended instead.