01 November, 2007

The Importance of Using Alt Tags

This entry was originally posted on the omnistaretools.com blog. It is reposted here for reference only.

Using alt tags on images is an important aspect of web design, for accessibility reasons. When designing a site, you should always take alt tags into account, simply because to not do so is to alienate an entire section of your audience.


It is sometimes hard to remember that a significant number of web users will interact with your site using something other than a normal configuration. Blind users often have software that will read out alt text in lieu of showing images; mobile viewers may not be able to view large images, and will instead browse your site according to alt tags; dial-up browsers generally turn off images when browsing unfamiliar sites, just to speed up surfing speed; high-tech users may be using a lynx browser to view your site; and e-mail clients almost always have images turned off as default. In each of these circumstances, the viewer will not see the images you put on your site, but just the alt text. Ignoring alt text would be to ignore the experience of these potential prospects on your site.
Thankfully, there is an easy way of fixing this. When placing an image on your site, just always remember to put in alt text describing what the image is, or what the image is for. That’s it. That’s the fix in its entirety.
(If you want to get technical for a moment, what this means is whenever you place a picture up (), just add in an alt description, as so: description. Of course, in reality you should also be putting in height and width attributes, but that’s a topic for a future article.)
That said, I need to also talk about the part of alt tags that I’ve been consciously omitting until now: alt tags in SEO.

Search engine optimization through alt tags?

In the past, alt tags were used in black hat SEO by stuffing in keywords that could not be seen by normal users into the alt tags. Back then, this was one of a number of techniques used to hide keywords from users while showing them to spiders indexing your site. Instead of a response to this misuse coming from search engines directly, browsers fought back by showing this text to ordinary viewers whenever a user hovered the mouse pointer over the image. But that all changed a couple of years back, when all the major search engines simultaneously decided to revise their ranking algorithms to specifically ignore all alt text content.
I’m going to repeat that to make sure it’s fully understood: Search engines do NOT consider alt text when determining your ranking. This means that keyword-stuffing your alt text is completely pointless. It does nothing to help you, and it does nothing to hurt you, in SEO terms. If all the web were just SEO, then I’d say to just forget about alt tags completely. But accessibility is also important, as if your site is accessible when your competitors’ are not, then that means you’ll get every sale that they lose due to their accessibility. And this is just as important, if not more so, than SEO.
Plus, who’s to say that next year search engines won’t start taking alt tags into consideration again?
A final related tip before I sign off for the day: consider using a description of your graphics beneath each picture. Research has shown that not only do prominent pictures receive a good percentage of users’ attention when they arrive on your site, but also any text right below that image, so long as it is clearly differentiable from the main content of the site (in italics, or small and bold). If you try this, do not eliminate alt text from the picture; but also try not to make the alt text a direct copy of the text below it. Use alt text to further describe the image, whenever possible.
And I really shouldn’t have to say this, but if you use an image that is not meant to be seen by the user (such as a whitespace image or similar), then do not enter in an alt tag. Nothing is more irritating to a blind websurfer than when every bulleted point starts off with the computer reading out “bullet point” in a robotic voice. Well… almost nothing. I guess webmasters who put white text on a white background filled with keywords is more irritating. But not by much, since you can generally just skip over paragraphs full of keywords, but if you want to hear each bullet point, then you’re pretty much forced to hear every instance of “bullet point” spoken aloud.
Posted by Eric Herboso.
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