Mozilla Developers

Developer tools, resources, videos and more

Firefox Quantum: Developer Edition

Get the latest features, fast performance, and the development tools you need to build for the open web.

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Developer resources

MDN

The best resource for the Open Web.

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Firefox DevTools

Edit and debug HTML, CSS, and JavaScript.

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WebAssembly

Use the .wasm format as a compiler target.

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Cross-browser testing

Easily test your site on every browser and operating system.

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Events to check out

Fresh from our blog

Fresh from our blog

  • MDN’s First Annual Web Developer & Designer Survey

    Today we are launching our first annual MDN Developer & Designer Needs Survey. Web developers and designers, we urge you to participate! This is your opportunity to tell us about your needs and frustrations with the web. Your participation will influence how browser vendors like Mozilla, Google, Microsoft, and Samsung prioritize feature development.

    Read more

  • Add-Ons Outage Post-Mortem Result

    We’ve been conducting an ongoing post-mortem on the add-ons outage that occurred earlier this year. There was a lot more digging to do than we expected. In addition to this updated high-level overview, we’ve also published our findings in detailed incident and technical reports that are now available.

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  • Testing Picture-in-Picture for videos in Firefox 69 Beta and Developer Edition

    Firefox has an experimental new UI feature in Firefox 69 Beta and Developer Edition – and Firefox engineers are looking for feedback on the implementation. Picture in Picture in the browser lets you pop a video out from where it’s being played into a special kind of window that’s always on top. Then you can move that window around or resize it however you need! Let us know what you think.

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Projects we love

A new layout system for the Web.

See grids in action

Mozilla’s next-generation web engine.

Get involved

A systems programming language that is fast and safe.

Check out Rust

Powerful Web technologies that help push games to the new level.

Learn more

Build exciting virtual reality Web pages using HTML.

Start building