If you’ve accessed the MDN website today, you probably noticed that it looks quite different. We hope it’s a good different. Let us explain! MDN has undergone many changes in its sixteen-year history from its early beginning as a wiki to the recent migration of a static site backed by GitHub. During that time MDN grew organically, with over 45,000 contributors and numerous developers and designers

Retrospective and Technical Details on the recent Firefox Outage On January 13th 2022, Firefox became unusable for close to two hours for users worldwide. This incident interrupted many people’s workflow. This post highlights the complex series of events and circumstances that, together, triggered a bug deep in the networking code of Firefox. What Happened? Firefox has a number of servers and rela

Introducing Firefox’s new Site Isolation Security Architecture Like any web browser, Firefox loads code from untrusted and potentially hostile websites and runs it on your computer. To protect you against new types of attacks from malicious sites and to meet the security principles of Mozilla, we set out to redesign Firefox on desktop. Site Isolation builds upon a new security architecture that ex

ES modules bring an official, standardized module system to JavaScript. It took a while to get here, though — nearly 10 years of standardization work. But the wait is almost over. With the release of Firefox 60 in May (currently in beta), all major browsers will support ES modules, and the Node modules working group is currently working on adding ES module support to Node.js. And ES module integra

tl;dr: Support for QUIC and HTTP/3 is now enabled by default in Firefox Nightly and Firefox Beta. We are planning to start rollout on the release in Firefox Stable Release 88. HTTP/3 will be available by default by the end of May. What is HTTP/3? HTTP/3 is a new version of HTTP (the protocol that powers the Web) that is based on QUIC. HTTP/3 has three main performance improvements over HTTP/2: Bec

State Partitioning is the technical term for a new privacy feature in Firefox called Total Cookie Protection, which will be available in ETP Strict Mode in Firefox 86. This article shows how State Partitioning works inside of Firefox and explains what developers of third-party integrations can do to stay compatible with the latest changes. Web sites utilize a variety of different APIs to store dat

In our previous post — MDN Web Docs evolves! Lowdown on the upcoming new platform — we talked about many aspects of the new MDN Web Docs platform that we’re launching on December 14th. In this post, we’ll look at one aspect in more detail — how we are handling localization going forward. We’ll talk about how our thinking has changed since our previous post, and detail our updated course of action.

To wrap up January, we are proud to bring you the release of Firefox 85. In this version we are bringing you support for the :focus-visible pseudo-class in CSS and associated devtools, <link rel="preload">, and the complete removal of Flash support from Firefox. We’d also like to invite you to preview two exciting new JavaScript features in the current Firefox Nightly — top-level await and relativ

After several intense months of work on such a significant change, the day is finally upon us: MDN Web Docs’ new platform (codenamed Yari) is finally launched! Between November 2 and December 14, we ran a beta period in which a number of our fabulous community members tested out the new platform, submitted content changes, allowed us to try out the new contribution workflow, and suggested improvem

Introduction We have enabled Warp, a significant update to SpiderMonkey, by default in Firefox 83. SpiderMonkey is the JavaScript engine used in the Firefox web browser. With Warp (also called WarpBuilder) we’re making big changes to our JIT (just-in-time) compilers, resulting in improved responsiveness, faster page loads and better memory usage. The new architecture is also more maintainable and

We’ve made a lot of progress on moving forward with MDN Web Docs in the last couple of months, and we wanted to share where we are headed in the short- to mid-term, starting with our editorial strategy and renewed efforts around community participation. New editorial strategy Our updated editorial strategy has two main parts: the creation of content pillars and an editorial calendar. The MDN write

As October ushers in the tail-end of the year, we are pushing Firefox 82 out the door. This time around we finally enable support for the Media Session API, provide some new CSS pseudo-selector behaviours, close some security loopholes involving the Window.name property, and provide inspection for server-sent events in our developer tools. This blog post provides merely a set of highlights; for al

Last week, Mozilla announced some general changes in our investments and we would like to outline how they will impact our MDN platform efforts moving forward. It hurts to make these cuts, and it’s important that we be candid on what’s changing and why. First we want to be clear, MDN is not going away. The core engineering team will continue to run the MDN site and Mozilla will continue to develop

Changes to SameSite Cookie Behavior – A Call to Action for Web Developers We are changing the default value of the SameSite attribute for cookies from None to Lax. This will greatly improve security for users. However, some web sites may depend (even unknowingly) on the old default, potentially resulting in breakage for those sites. At Mozilla, we are slowly introducing this change. And we are str

At Mozilla, we want the web to be capable of running high-performance applications so that users and content authors can choose the safety, agency, and openness of the web platform. One essential low-level building block for many high-performance applications is shared-memory multi-threading. That’s why it was so exciting to deliver shared memory to JavaScript and WebAssembly in 2016. This provide

Background: RegExps in SpiderMonkey Regular expressions – commonly known as RegExps – are a powerful tool in JavaScript for manipulating strings. They provide a rich syntax to describe and capture character information. They’re also heavily used, so it’s important for SpiderMonkey (the JavaScript engine in Firefox) to optimize them well. Over the years, we’ve had several approaches to RegExps. Con

Editor’s Note: April 6, 7:00pm pt – After some more investigation into this problem, it appears that the initial analysis pointing to the Content-Disposition was based on bad information.  The reason that some browsers were not caching direct messages was that Twitter includes the non-standard Pragma: no-cache header in responses. Using Pragma is invalid as it is defined to be equivalent to Cache-

Threats to users’ privacy and security are growing. At Mozilla, we closely track these threats. We believe we have a duty to do everything we can to protect Firefox users and their data. We’re taking on the companies and organizations that want to secretly collect and sell user data. This is why we added tracking protection and created the Facebook container extension. And you’ll be seeing us do m

Standardizing WASI: A system interface to run WebAssembly outside the web Today, we announce the start of a new standardization effort — WASI, the WebAssembly system interface. Why: Developers are starting to push WebAssembly beyond the browser, because it provides a fast, scalable, secure way to run the same code across all machines. But we don’t yet have a solid foundation to build upon. Code ou