88 posts tagged “firefox”
Mozilla's Firefox browser.
2025
Backstory on the default styles for the HTML dialog modal. My TIL about Styling an HTML dialog modal to take the full height of the viewport (here's the interactive demo) showed up on Hacker News this morning, and attracted this fascinating comment from Chromium engineer Ian Kilpatrick.
There's quite a bit of history here, but the abbreviated version is that the dialog element was originally added as a replacement for window.alert(), and there were a libraries polyfilling dialog and being surprisingly widely used.
The mechanism which dialog was originally positioned was relatively complex, and slightly hacky (magic values for the insets).
Changing the behaviour basically meant that we had to add "overflow:auto", and some form of "max-height"/"max-width" to ensure that the content within the dialog was actually reachable.
The better solution to this was to add "max-height:stretch", "max-width:stretch". You can see the discussion for this here.
The problem is that no browser had (and still has) shipped the "stretch" keyword. (Blink likely will "soon")
However this was pushed back against as this had to go in a specification - and nobody implemented it ("-webit-fill-available" would have been an acceptable substitute in Blink but other browsers didn't have this working the same yet).
Hence the calc() variant. (Primarily because of "box-sizing:content-box" being the default, and pre-existing border/padding styles on dialog that we didn't want to touch). [...]
I particularly enjoyed this insight into the challenges of evolving the standards that underlie the web, even for something this small:
One thing to keep in mind is that any changes that changes web behaviour is under some time pressure. If you leave something too long, sites will start relying on the previous behaviour - so it would have been arguably worse not to have done anything.
Also from the comments I learned that Firefox DevTools can show you user-agent styles, but that option is turned off by default - notes on that here. Once I turned this option on I saw references to an html.css stylesheet, so I dug around and found that in the Firefox source code. Here's the commit history for that file on the official GitHub mirror, which provides a detailed history of how Firefox default HTML styles have evolved with the standards over time.
And via uallo here are the same default HTML styles for other browsers:
2024
In 2021 we [the Mozilla engineering team] found “samesite=lax by default” isn’t shippable without what you call the “two minute twist” - you risk breaking a lot of websites. If you have that kind of two-minute exception, a lot of exploits that were supposed to be prevented remain possible.
When we tried rolling it out, we had to deal with a lot of broken websites: Debugging cookie behavior in website backends is nontrivial from a browser.
Firefox also had a prototype of what I believe is a better protection (including additional privacy benefits) already underway (called total cookie protection).
Given all of this, we paused samesite lax by default development in favor of this.
[On WebGPU in Firefox] There is a lot of work to do still to make sure we comply with the spec. in a way that's acceptable to ship in a browser. We're 90% of the way there in terms of functionality, but the last 10% of fixing up spec. changes in the last few years + being significantly more resourced-constrained (we have 3 full-time folks, Chrome has/had an order of magnitude more humans working on WebGPU) means we've got our work cut out for us. We're hoping to ship sometime in the next year, but I won't make promises here.
Experimenting with local alt text generation in Firefox Nightly (via) The PDF editor in Firefox (confession: I did not know Firefox ships with a PDF editor) is getting an experimental feature that can help suggest alt text for images for the human editor to then adapt and improve on.
This is a great application of AI, made all the more interesting here because Firefox will run a local model on-device for this, using a custom trained model they describe as "our 182M parameters model using a Distilled version of GPT-2 alongside a Vision Transformer (ViT) image encoder".
The model uses WebAssembly with ONNX running in Transfomers.js, and will be downloaded the first time the feature is put to use.
2020
New developer features in Firefox 75 (via) Firefox 75 just came out with a bunch of new developer features. My favourite is instant evaluation in the JavaScript console: any statement without side effects now shows a preview of its results as you type.
2019
selenium-demoscraper (via) Really useful minimal example of a Binder project. Click the button to launch a Jupyter notebook in Binder that can take screenshots of URLs using Selenium-controlled headless Firefox. The binder/ folder uses an apt.txt file to install Firefox, requirements.txt to get some Python dependencies and a postBuild Python script to download the Gecko Selenium driver.
This paper introduces Mesh, a plug-in replacement for malloc that, for the first time, eliminates fragmentation in unmodified C/C++ applications. Mesh combines novel randomized algorithms with widely-supported virtual memory operations to provably reduce fragmentation, breaking the classical Robson bounds with high probability. Mesh generally matches the runtime performance of state-of-the-art memory allocators while reducing memory consumption; in particular, it reduces the memory of consumption of Firefox by 16% and Redis by 39%.
Since Mozilla moved on from Firefox OS, its derivatives have shipped on an order of magnitude more devices than during its entire time under Mozilla’s leadership and it has gone on to form the basis of the third largest and fastest growing mobile operating system in the world.
2017
Boiling the Ocean, Incrementally—How Stylo Brought Rust and Servo to Firefox. Firefox Quantum is the product of an impressive, highly risky chain of software engineering—Rust, Servo, then Stylo.
Firefox Debugger Playground. Excellent hands-on tutorial to using the Firefox JavaScript debugger. I learned a bunch of neat tricks from this—including using conditional breakpoints to add temporary console.log statements—since that function returns undefined it won’t pause your code, but this saves you from having to remember to remove the lines from your source code later. I also didn’t know that the Firefox debugger can show the value of variables in paused code if you hover over them in the source pane. [UPDATE: Turns out Chrome DevTools do this as well—TIL]
Verified cryptography for Firefox 57 (via) Mozilla just became the first browser vendor to ship a formally verified crypto implementation.
Entering the Quantum Era—How Firefox got fast again and where it’s going to get faster. I’ve been trying out the beta of Firefox 57 and it’s fantastic. All of that work on Servo and Rust is definitely paying off!
Saying Goodbye to Firebug. Firebug has reached end-of-life as a separate extension, replaced by the built-in Firefox Developer Tools. It’s hard to overstate how influential Firebug has been in helping to turn front-end web development into a respected and productive engineering discipline.
2013
What data structures are used to implement the DOM tree?
You may enjoy this post from Hixie back in 2002 which illustrates how different browsers deal with incorrectly nested HTML. IE6 used to create a tree that wasn’t actually a tree! http://ln.hixie.ch/?start=103791...
[... 49 words]2010
Firefox 4: the HTML5 parser—inline SVG, speed and more. A complete replacement for the oldest part of Gecko (the HTML parser dates back to 1998) headed up by HTML5 validator author Henri Sivonen, using the parsing algorithm defined in the HTML5 specification. Improvements include parsing taking place off the main UI thread and the ability to embed SVG and MathML directly inline in HTML pages.
Plugging the CSS History Leak (via) Firefox is fixing the nefarious CSS visited link colour history leak flaw, which currently affects all browsers and allows a malicious site to determine if you have visited a specific site by checking getComputedStyle against a link to that page. It’s an obtrusive but necessary fix—visited link styles will be restricted to colour and border styles (no background images and hence no more checkbox effects since the image request could leak information) and those colours will not be reported via getComputedStyle. I hope other browser vendors follow suit.
HTML 5 audio player demo. Scott Andrew’s experiments with the HTML5 audio element (and jQuery)—straight forward and works a treat in Safari, but Firefox doesn’t support MP3. Presumably it’s not too hard to set up a fallback for Ogg.
2009
HTML 5 Parsing. Firefox nightlies include a new parser that implements the HTML5 parsing algorithm (disabled by default), which uses C++ code automatically generated from Henri Sivonen’s Java parser first used in the HTML5 validator.
Firefox 3.5 for developers. It’s out today, and the feature list is huge. Highlights include HTML 5 drag ’n’ drop, audio and video elements, offline resources, downloadable fonts, text-shadow, CSS transforms with -moz-transform, localStorage, geolocation, web workers, trackpad swipe events, native JSON, cross-site HTTP requests, text API for canvas, defer attribute for the script element and TraceMonkey for better JS performance!
Browsing my browsing. Roo Reynolds used the MeeTimer Firefox extension to gather statistics on his browsing habits, then extracted data directly from the SQLite database and generated his own graphs using PHP and the canvas element.
Pwn2Own trifecta: Hacker exploits IE8, Firefox, Safari. You just can’t trust browser security: Current versions of Safari, IE8 and Firefox all fell to zero-day flaws at an exploit competition. None of the vulnerabilities have been disclosed yet.
Magic properties make Firefox synchronously load the Java plugin. Even defining a function called sun() (or several other symbols) will trigger the Java VM to be loaded, dramatically hurting the performance of your page.
Open in Browser Firefox Add-on (via) Solves the “application/json wants to download” problem, among others.
FireScope. Neat little Firefox / Firebug extension which adds a “Reference” tab showing documentation for the selected element from the comprehensive SitePoint Reference site.
2008
ReferenceError: console is not defined. Since Firebug 1.2 you need to call window.loadFirebugConsole() in order for console.log and friends to work.
Browser Paint Events. The latest Firefox nightlies include a new MozAfterPaint event which fires after a portion of the page has been redrawn and provides co-ordinates of the affected rectangle. John Resig provides a neat bookmarklet that uses the new event to visualise repainting operations.
querySelectorAll in Firefox 3.1. John Resig benchmarks the various JavaScript libraries’ support for querySelelectorAll, and finds an impressive 2-6x performance improvement over native DOM traversal. It’s worth clicking through to John’s experimental plugin for adding support to jQuery, which does a clever trick using __proto__ to convert the collection returned by querySelectorAll in to a jQuery object in browsers that support it.
eval() Kerfuffle. The ability to read supposedly private variables in Firefox using a second argument to eval() will be removed in Firefox 3.1.
Javascript protocol fuzz results. If your HTML sanitizer uses blacklisting rather than whitelisting here are a few more weird ways of injecting javascript: in to a link that you need to worry about—but you should really switch to whitelisting http:// and https:// instead.
Module Pattern Provides No Privacy... at least not in JavaScript(TM) (via) JavaScript variables hidden inside a closure aren’t as hidden as I thought—it turns out you can pass a closure as the second argument to eval (at least in Firefox) and “steal” private variables back out of it.