EDIT – March 21 2015 – This article is really old now, so please take what it says with a pinch of salt!
One of the questions I’ve often been asked about SEO is this:
“Does the wording we put in image Alt text get used in Google’s rankings?”
The answer to this question seems to have changed over the years, where first it seemed to be a really popular place for web developers to sneak in a few additional SEO keywords into their page. The text would be hidden from view but Google would read it inline as actual content of the page. Was this good practise? Absolutely not! It’s a form of keyword stuffing and isn’t advised.
The reason for this being a bad thing to do on your website was that it made absolutely no sense to blind people who use a screen reader to have the page content read out to them. When they encounter an image on a page, they’ll expect to hear the image alternative text, but instead they get a list of your company keywords – that’s not very nice is it?
So Google realised this, and started ignoring Alt text used in images. Quite simply, Alt text is not supposed to be used for SEO, and that’s fair enough – don’t you think?
But the thing is, lately it’s been proven that Google does use it in ranking, and treats it just like it treats your page content. So in terms of SEO, it’s not as important as text in your <title> tag, or your <h1> tag, but it is still used nonetheless.
In fact, to prove this I did a test in Google using an example website we used in an SEO experiment a while ago, frictionless-owls.com (you can see our written reports on the experiment here). I added some unique words into the Alt text of some images (it’s harder than you think to come up with a unique word that doesn’t bring up results in Google!) and waited hesitantly for Google to index the page and find my new words.
I checked by googling for these keywords every week, and by the third week both keywords brought up the frictionless owls website. I assume it took a while for Google to re-spider the site because it’d been static for so long, so didn’t hurry back to check for new content (something we reported on in the original SEO challenge article).
So back to my original question, does the wording we put in an image Alt text get used in Google’s rankings, yes, yes it does. But it shouldn’t, so don’t go keyword stuffing!