Google’s John Mueller recently stated in a webmaster hangout that W3C validation has no impact on search results.
Mueller was asked whether W3C validation errors could slow down the time it takes to download a page.
In response, Mueller says W3C validation has no impact on the time to download a page, and has no impact on a website in search results in general.
“No, this does not affect time to download a page. Time to download a page is purely the time that it takes from Googlebot asking your server for a URL, to your server having provided that full content to Googlebot.
What is on that page is totally irrelevant, other than maybe if you have a lot of text then maybe it will take a long time to transfer. But HTML errors are totally irrelevant for that.”
As it relates to search results, Mueller says this about W3C validation:
“In general, the W3C validation is something that we do not use when it comes to search. So you don’t need to worry if your pages kind of meet the validation bar or not. However, using the validation is a great way to double check that you’re not doing anything broken on your site.”
Although there is no impact on search results, Mueller does recommend using the W3C validator for other reasons. One reason that Mueller didn’t mention, however, is there are laws around website accessibility in the United States.
Here’s why Mueller recommends using the W3C validator:
“So, in particular, for other kinds of devices for people who need accessibility features, the W3C validator is a great way to kind of get a confirmation that the markup you’re providing is pretty reasonable, and is something that most consumers of markup will be able to understand well.
So I definitely recommend checking out the validator tool and trying it on your pages and seeing what the results are, and then trying to improve things so you’re a little bit more in line with valid HTML.
That generally makes things a lot easier when it comes to displaying your pages, when it comes to understanding the content on your pages for things like screen readers. All of that makes it a lot easier if you have reasonable HTML.”
Hear Mueller’s full response below, starting at the 42-minute mark: