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Comment by aylmao | Hacker News Reader

I bumped into the acid3 test, and I noticed it didn't pass in Chrome anymore. Would anyone have any context as to why this is? It's a little bit odd to me that backwards compatibility was broken in at least 3 ways here.

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Acid3 was not updated when people decided to change the specifications. There are 3 things that are known to fail. Two of them are related to one change (see https://github.com/whatwg/dom/issues/319#issuecomment-296345... for details on that change). The third test is one where Acid3 mandates something that every browser did but was wrong per the specification, and it took several years for people to notice (see https://bugzilla.mozilla.org/show_bug.cgi?id=1311329 for some more details).

The Acid3 test on that website is officially unmaintained: https://lists.w3.org/Archives/Public/www-archive/2017Jul/000...

You can click/tap on “Acid3” after the test is done and get some details.

E.g. on my phone (iPhone, up-to-dare, I think) which scored 98/100 I get:

Failed 2 tests. Test 23 failed: expected '14' but got '5' - wrong exception for createElementNS('null', ':div') Test 25 failed: wrong exception Total elapsed time: 0.49s

The first one means it passed invalid parameters to createElementNS and expected a NamespaceError (14) exception but an InvalidCharacterError (5) exception occurred instead.

(I’m waiting at the drs office, and am happy to pass the time looking up error codes.)

The modern "standard" is what's called "living". Which means that any part of it can change at any time. This is unlike the old standards that were fixed (if not always adhered to).

Browsers aim to be backwards compatible with popular or influential sites, not synthetic tests.

I don't know because this isn't my area of expertise, but when I use my Firefox browser to load the page with the developer console open, it throws two XML parsing errors.

So I figure it's one of three things going on here. One, modern browser makers just don't bother testing Acid3 anymore, and bugs have crept into the browser. Two, modern browsers knowingly break Acid3 because they prefer to implement performance enhancements that are not strictly compliant with standards. Three, updated standards have added syntax or rules that invalidate some of the strange stuff that is packed into Acid3.

ACID has always been about testing obscure edge cases and weird parts of the HTML spec, and sometimes the way that the spec was written in the past differed from "in-the-wild" behavior. These days, in the post-W3C era, the HTML specs try hard to capture behavior as seen in-the-wild. Basically, ACID doesn't test the modern spec.

See, for one example: http://www.howtocreate.co.uk/SGMLComments.html#simple

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