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As someone who's been quite heavily involved with web-platform-tests, I'd caution against any use of the test pass rate as a metric for anything.

That's not to belittle the considerable achievements of Ladybird; their progress is really impressive, and if web-platform-tests are helping their engineering efforts I consider that a win. New implementations of the web platform, including Ladybird, Servo, and Flow, are exciting to see.

However, web-platform-tests specifically decided to optimise for being a useful engineering tool rather than being a good metric. That means there's no real attempt to balance the testsuite across the platform; for example a surprising fraction of the overall test count is encoding tests because they're easy to generate, not because it's an especially hard problem in browser development.

We've also consciously wanted to ensure that contributing tests is low friction, both technically and socially, in order that people don't feel inclined to withhold useful tests. Again that's not the tradeoff you make for a good metric, but is the right one for a good engineering resource.

The Interop Project is designed with different tradeoffs in mind, and overcomes some of these problems by selecting a subsets of tests which are broadly agreed to represent a useful level of coverage of an important feature. But unfortunately the current setup is designed for engines that are already implementing enough feature to be usable as general purpose web-browsers.

The tweet mentions that this is an arbitrary metric thrust upon them by Apple, so I don’t think they would necessarily disagree with you. During the monthly updates they do also show the passing number of tests without including the encoding tests because of how much they skew things.
Could a hand-picked subset be selected to make that metric?
Everything you said sounds very reasonable, yet the "Browser-Specific Failures" graph on the main page of the wpt.fyi website explicitly misleads us into thinking

PS I'm a big fan of the work and appreciate what you do. I check the interop page about once a week!

As someone who's been quite heavily involved with having a brain, I'd advocate for using of the test pass rate as a metric for how many tests are passed.
Why are you bringing this up, when it’s not been implemented as a metric here, but because Apple requires it for iOS.
Then talk to apple. They are the ones who put this bar in place.
I think it’s just fantastic that the Ladybird browser is close to being usable. I was under the impression this was going to take many years before it became competitive.
While I haven't tried it myself, I've seen a few of the monthly summaries videos. Passing the tests and being fast enough for daily usage is two very different things and right now Ladybird doesn't appear to be all that speedy.

Still an amazing feat of development from the entire team.

Three years ago I was very skeptical of Ladybird. But two things have changed. First, they have funding for 8 full time engineers, which I definitely wasn’t expecting. Second, it’s been three years. So given that, I am more optimistic.

There’s still a very long way before they can compete with Chrome, of course. And I’m not sure I ever understood the value proposition compared to forking an existing engine.

I do wonder if it's the case of "90% of completeness takes 90% of time; the remaining 10% takes another 90%".

Though, I suppose even if true, it would still be a pretty good timeframe.

Don't hold your breath though. Looking at the September progress report[0] there are many many things to iron out. It's great progress but there are still several years of development for LB to be ready.

[0] https://www.youtube.com/watch?v=6vsjIIiODhY

It really goes to show what a dedicated team can accomplish. Before Ladybird it was taken for granted that building an entirely new browser engine would take decades and people would laugh at you for even bringing it up.
I've started using it for some websites. It's surprisingly very capable already.
Don't worry. If the web browser ever becomes fast enough to be usable, even more javascript crap will be dumped on every website to slow it back down again
The linked tweet notes that this is an important milestone in getting Ladybird considered as an alternative browser engine in iOS.
Good context for why "Apple" is in the headline
...in the EU at least, anywhere else Apple is going to say "no" regardless of how good your engine is.
Super impressive that an independent, non-corpo project has gotten this far this quickly.
It is nuts, when you think about how much a browser does, it is a crazy feat.

Just building a good html/css renderer and a JS engine is crazy, but now you are hooked into the ecosystem and at the mercy of whatever comes next. Chrome can push back against proposals but little browsers either use chromium or are basically in a riptide trying to make sure they keep up.

I know what you meant by "non corpo", but the Ladybird organization is literally a corporation: https://ladybird.org/assets/documents/public-records/2024-03...
Definitely... IF they keep this up, they will be a real contender by the end of 2027. I keep saying I'd like to see a similar push for Servo though... since it's probably the next most feature-rich engine option. It really needs a corresponding browser project to go along side it though, since FF/Mozilla isn't that interested.
Are they really non-corpo? I remember seeing some corpos bankrolling it?

And in that sense, is it better than Gecko with firefox, which is non-profit?

But how to pass tests securely, is completely different problem. This is conformance testing. But impressive regardless.
> Super impressive that an independent, non-corpo project has gotten this far this quickly.

Well, it could be that AI actually speeds up development, who knows.

cloudflare is sponsoring. says it all.
I just tried building and running it. Surprisingly many websites already load fine, though Youtube doesn't and Vimeo/Reddit comment section crashed it. Still, the results are quite encouraging! It takes ~6GB of HDD to build it.
I wonder how hard the last 10% will be? If its a typical software project its going to be 90% more effort for the last 10%.
What's the security story in Ladybird? Do they use sandboxes etc? I'm a bit concerned that hundreds of thousands of lines of C++ browser code written in just three years could be a minefield, but I hope I'm wrong.
If nothing else, having an alternative engine with any amount of viability at all that isn't Blink is great news. I'll be interested to see how this progresses.
There is a big jump in the graph! I wonder what contributed to that big improvement.
The WPT score is a flawed metric (encoding tests are overweighted), but it's one of the few objective yardsticks we have. What matters more is that Ladybird is finding spec ambiguities by implementing from scratch rather than cargo-culting Chrome's behavior. The real test isn't passing 90%—it's whether they can keep pace as the web platform adds new APIs faster than any independent team can implement them. Browser engine development has become a regulatory moat, and breaking it requires either massive funding or accepting permanent incompatibility with the "modern web." Still rooting for them. Browser monoculture is worse than metric gaming.
The WPT score is a flawed metric (encoding tests are overweighted), but it's one of the few objective yardsticks we have. What matters more is that Ladybird is finding spec ambiguities by implementing from scratch rather than cargo-culting Chrome's behavior.

The real test isn't passing 90%—it's whether they can keep pace as the web platform adds new APIs faster than any independent team can implement them. Browser engine development has become a regulatory moat, and breaking it requires either massive funding or accepting permanent incompatibility with the "modern web."

Still rooting for them. Browser monoculture is worse than metric gaming.

It's always struct me as interesting that ladybird is built with C++. I like C++, and prefer it to languages like Rust, but it's not uncommon to see new OSS projects using weird languages and the newest tools. Lots of languages offer improvements in regards to threading models, development speed, or cross-platform support which we don't get in C++.

I suppose their success is likely directly related to the fact they made reasonable, practical development choices, but still.

What JS engine does it run on?
Me as engineer: it's wild a big corporation dictates a quality bar and limit API access for 3rd party software.

Me as customer: oh man I'm sure glad stuff is reviewed to some quality bar and the OS limits API access.

So was there any app with an alternative browser engine already approved by Apple?
Now that 90% of the work is done, it is only 90% of the work that remains :)
Thank you for the belly-laugh. It's Goodhart's Law in graph form.

"Oh, is this metric important? Let me get right on that."

No shade intended towards the Ladybird team. You were given the terms and you're behaving rationally in response to them. More power to you. It's just a fantastic demonstration of what it looks like to very suddenly be developing against a very specific metric.

How's the ladybird gtk stuff coming along?
Oh yes cus Apple really care about the web.
You love to see it
OT, but I really like the name Ladybird for a silly reason - it's the name of Hank Hill's dog. Whenever I hear it I think of her and smile. That's right, the thought of a cartoon dog makes me happy. I told you it was silly.
I wish them well, but browsers are very much pay-to-play. Google had to pay their way to their current dominant position.
Along the same lines, the State of Utopia will be building a free web browser for everyone, once AI is strong enough to do so. Please feel free to vote on feature ideas here: https://pollunit.com/polls/ahysed74t8gaktvqno100g