Why Isn't the <html> Element 100% Supported on

February 02, 2024

I saw a Mastodon post that made me laugh this morning. It seemed sort of crazy that the html element wouldn’t have 100% support on Heck, I’ve been using it since 1994 and it worked just fine back then! This led me down a bit of a rabbit hole.

A bit of background, first. Can I Use… is a site that helps web developers track the adoption rate of web technologies. It estimates browser usage, measures feature compatibility, and spits out a number that tries to reflect how available a feature is. It’s a site I’ve been using almost since it launched in 2010 and I’ve always found it really useful.

So why is it currently saying the html element only has 97.34% support? That’s less than the current support percentage for the audio element! It also looks like the same is true for the a and p elements with exactly the same 97.34% support number.

One thing I learned when looking into this is that a lot of the data on the site actually comes from MDN 1. MDN is another resource I use and trust, so this seems reasonable to me. It also often has stats about feature uptake, so it makes sense for to piggyback on that.

Looking at the MDN page for the html element, it has a browser compatibility section. In that are two rows with a lot of red Xs. The first is for the optional manifest attribute on the html element. This is deprecated and was never standardized. The second is the related “secure context required”, which is an Editor’s Draft — that is, not something currently on the standardization track. I don’t know how this was previously related to the html element, but that use was also never standardized and is deprecated.

So, there are two features listed here that almost all browsers correctly do not support. But still, it doesn’t look like this is the reason for the missing 2.66%. There are some browsers that are listed as “Support Unknown”. Adding up all the current usage for these browsers comes to 1.27%. There’s also an entry for Android Browser versions 2.1–4.3 which is listed as not supporting the html element — which I find highly dubious — but it’s listed as having a usage share of 0%. I suppose there might be some rounding errors here that would bump the 1.27% to 2.66%? But I still find this very unclear. Also, I feel very confident that those older browsers supported the html element!

So yeah, I don’t have a great answer for this. If you do, please let me know! I’ve always taken the numbers from with a few grains of salt, but I’ll be adding a few more going forward. I still think it’s a great resource.

UPDATE: rezonant on Mastodon poked me to let me know that he posted a comment on Hacker News that has a possible explanation. The short version: if you switch to “% of all tracked” in the top right beside “usage”, and then add up the “support unknown” browser number, you get 99.98%. It’s a lot easier to see how rounding errors could make this the correct number. Still, I think the way older browsers are handled here is confusing. It doesn’t affect the overall number too much, but in the case of base level elements like html, it seems odd.

  1. MDN used to stand for Mozilla Developer Network. Now it’s just MDN. I spent a few minutes looking on the MDN site to see if I could find any mention of the full name, but I guess they’re just all in on “MDN” now.