Ever struggled to get heading tags right in includes/components? headingoffset could be the answer…
Firefox for Web Developers
@firefoxwebdevs
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Official Firefox account for people who build on the web. Learn about the things we're working on to grow and improve the web platform.
We're experimenting with a way to visualize session history in Firefox DevTools, and we'd love your feedback!
Here's the background, and how to try it: https://blog.farre.se/posts/2026/06/01/session-history-diagrams/
The Web Serial API landed in Firefox 151, allowing you to connect directly to microcontrollers, dev boards, 3D printers, power meters, and other serial-connected hardware from the web. Here's how it works:
CSS style() queries landed in Firefox 151 making them newly available across engines. Here's how they work:
Correction: Chrome's doesn't use the cloud, it only uses the 4gb model.
chrome://on-device-internals/ has a faulty "uninstall" feature, which made it look like the model was uninstalled, but it still worked, which made me think it (as the spec allows) was using the cloud.
Chrome shipped an LLM Prompt API to the web platform. At Mozilla, we oppose this API. Here's why:
CSS's light-dark() now accepts images, making it simpler to define alternate values for a dark color scheme. Here's how it works:
sizes="auto" landed in Firefox 150, making responsive images simpler and more reliable. Here's when you can use it, and how…
map.getOrInsertComputed is newly baseline! It's a small feature, but I've found it pretty useful. Here's how it works.
Full docs and polyfills on MDN https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/WeakMap/getOrInsertComputed
CSS contrast-color is newly baseline, but it falls short in some areas. Here's how it works, and what to look out for: