One common suggestion concerning the search optimization of images is to use the alt
attribute to place keywords relevant to the image contents.
I really loathe this.
If it was an amazing, perfect, incredible search optimization technique which would bring absolutely fantastic traffic I still wouldn’t recommend the technique. Appropriate alt attributes are one of the most critical areas for the user experience of screen reader users — using them inappropriately is a great way to give this section of your market a horrible experience on your site.
To be perfectly clear — most advocates of use of the alt
attribute for image optimization do not advocate keyword stuffing or any other serious abuse of the alt
attribute. However, to me, any recommended use of the attribute which does not place the user first is problematic.
Bluntly, if it’s really important that an image is described, then you should describe it in plain text, written out in a presentable and understandable manner. In the site content — not buried in the code.
I’m a firm believer that most images are purely decorative. They provide little to no information to a screen reader user, and the best choice is to leave the alt
attribute empty. This means that the user agent can completely ignore the image — they can identify that there is an image present, and will also be aware that it does not need to be dealt with. (WebAIM: Designing for screen reader compatibility.) An absent alt
attribute is dealt with differently — the user agent will attempt to identify the image via the src
attribute:
How the JAWS screen reader announces image information
The behaviours detailed apply to JAWS version 6.2, 7.0, 7.1 and 8.0.
- default behaviour for image with an
alt
attribute containing text- Announces presence of the image and the alt text
- default behaviour for null alt text
alt=""
- Does not announce the presence of the image
- default behaviour for an img without an
alt
attribute- Does not announce the presence of the image
- default behaviour for image with an alt attribute containing text in a link
- Announces presence of the image and the alt text
- default behaviour for null alt text in a link
alt=""
- Does not announce the presence of the image
- default behaviour for an img without an
alt
attribute in a link- Announces the presence of the image and the value of the
src
attributeSteve Faulkner (Investigating the proposed alt attribute recommendations in HTML (HyperText Markup Language) 5)
Now, the src
attribute can be useful in certain situations – a well-named image file can be quite clear from this perspective. However, leaving the alt attribute blank will provide the best experience for insignificant images.
Significant images, on the other hand, are a completely different story. They do say that an image is worth 1,000 words…is it possible to do realistic justice to any significant image in an alt
attribute?
My general take is that there are three types of images on the web:
- Content-bearing text images,
- Content-bearing non-text images,
- and decorative images
The first is the only category which should have content in the alt
attribute — and that text should be an exact duplicate of the text portrayed in the image. The second category should have additional descriptive information provided in the text, or a clear and obvious link provided to a more thorough description. The third should be left with an empty alt
attribute. This is not significant information, and it should remain the user’s prerogative to enable the screen reader option which will provide them with additional image information.
The question with images and accessibility isn’t precisely a debate between whether images are content or not — instead, it’s the question whether images are useful content to those users with visual disabilities. The question you need to ask yourself is whether an alt
attribute on the image will provide useful information to a user. Is it helpful to mark an image as “my cat” or “landscape of mountains with a flower in the foreground,” or does it simply add noise to the content?
This isn’t to say, however, that there aren’t perfectly reasonable ways to optimize for image search which won’t also interfere with the user experience with your website. Liana Evans recently published an article discussing image optimization at Search Engine Guide.
She does suggest using the alt
attribute, but does at least emphasize moderation and specifically mentions accessibility as an issue to consider. The other four suggestions are all very sensible and simple ways to ensure that your images are available and easy to find. Li doesn’t mention the content surrounding the images in this article, although she does mention it in a Cre8asiteForums thread on image optimization. In this thread, Li specifically mentions that alt
attribute use for image optimization is only a very slight influence.
On the whole, accessibility should always trump marketing. However, there really isn’t a huge divide between the two. In any circumstances I can imagine, there’s no search marketing benefit to choosing a less-accessible solution. Perhaps you’ll be less able to take advantage of some search engine loophole. This isn’t a serious loss for most businesses — there’s no guarantee that the same loophole will still be around next month, anyhow.
Further resources:
It’s important to note that these resources are intended to provide you with a wide variety of viewpoints on the subject. I think these articles are all worth reading; I don’t necessarily agree with them on every point.
Alt Attribute Use
- Mike Cherim: Alt and Accessibility
- Dive Into Accessibility: Providing Text Equivalents for Images
- 456 Berea Street: The Alt and Title Attributes
- Simon Willison, Guild of Accessible Web Designers: Writing Good Alt Text
Joe Dolson
It’s true that there are some SEO consultants who specifically mention that they are no longer effective; but it’s equally true that equally well-respected SEO consultants still say that they are.
My point is that it doesn’t matter to me whether it’s an effective technique. It’s not worth the accessibility cost.
chi loop
Nice article Joe.
And regarding the usage of alt tags for SEO, they used to be effective a really long time back, till it was noticed by search engines their heavy misuse for spam purposes. When talking about stuff on SEO, there’s a lot of vague stuff people say on the web. Not wanting to fall in that category, while I don’t remember any links to the sources I’d read for the fact that they once used to be effective, here are two links below to content by respected SEO consultants mentioning that alt tags are no longer effective for SEO.
How Important is ALT Text In Search Engine Optimization?
IL 2006: Wednesday Keynote: Web Presence for Internet Librarian
Shari Thurow
Joe Dolson
Thanks, Mike. The whole natural issue really gets me. If information is important enough for anybody, it should be important enough for everybody.
There are always pieces of information which are truly targeted at specific audiences, but that’s only a tiny portion of what needs to be present on any site.
Mike Cherim
Love it, Joe. This coincides perfectly with my feelings on the matter, especially in that an image is seldom anything more decoration, and if it’s not, if it has value, then the surrounding text is the most reasonable, effective, and natural way of telling the mind’s eye of the reader, sighted or otherwise, what to see.
Bookmarking this one in Ma.gnolia 🙂
Joe Dolson
I don’t mind using appropriate attribute text when necessary; it’s simply that most of the time, nothing at all is what I would recommend for best usability for screen reader users…
I know that many people will use reasonable attribute values without prompting; others will use empty phrases like “decorative graphic.” I’d certainly prefer something meaningful — and most meaningful phrases are likely to contain relevant keywords.
What I know, however, is that many people take any suggestion of keyword use as a commandment, and will start to use them in places where they simply aren’t appropriate.
I’d hope to help prevent that…
Joost de Valk
Over-optimizing anything is never good for anyone. I strongly agree with you: use the alt tag for what it SHOULD do an include relevant content in it when necessary. You don’t have to shy away from using a nice keyword if it’s relevant though 🙂