Alt text is an important yet occasionally overlooked part of making a site accessible to all users.
What is alt text?
Alt text is a simple bit of HTML code that essentially describes an image that appears on a web page so that the user still knows what the image represents if they are visually impaired or if the picture simply doesn’t display correctly.
The alternative attribute can be input within the ‘alt text’ or ‘alt tag’ of the image element and the exact wording used depends on the context of the image as much as the content itself.
An additional benefit is that it provides a semantic description of images for search engines. This can attract additional traffic through Google Images and has a positive impact on SEO.
According to Google, it “uses alt text along with computer vision algorithms and the contents of the page to understand the subject matter of the image. Also, alt text in images is useful as anchor text if you decide to use an image as a link”.
Matt Cutts of Google discusses alt text further in this useful video.
To be clear, alt text is not going to suddenly help a site climb to the top of search results, instead it is one of a number on-page factors that contribute to improved SEO performance. Think of it as good housekeeping.
To help explain this in more detail, here are the basics of using alt text for images…
Keep the alt text short
In general a literal, concise alt tag is the best option, though it may be suitable to write a more descriptive tag if the type of image used is important to the context of the article.
For example, it may be necessary to describe what is taking place in the image, or label it as a particular photo or painting by a known artist.
However alt text that is too long or floral loses the impact of a short description and may mean that it isn’t indexed as efficiently.
Try to mention the topic of the page in alt text
Alt text is an effective way of telling Google the topic of the page and therefore giving it an extra boost in search rankings.
Therefore if a page is about Snoopy, then it will be of SEO benefit to include an image of the lovable cartoon character with alt text as ‘alt= “snoopy”’.
That said, it’s not a good idea to repeatedly use the same alt text so try to mix it up and ensure that the alt attribute is relevant to that particular image.
Which leads me to my next point…
Avoid keyword stuffing
Google’s dislike for keyword stuffing extends to alt text as well, so it is to be avoided at all costs.
You’re unlikely to score any points for describing an image of a men’s hoodie as ‘hoodie mens hoodie male hoodie mens blue hoodie’.
A simple description will suffice and will avoid any nasty Google penalties.
Be precise in alt text for products
For ecommerce, alt text should precisely describe the product within the image so that it shows up in relevant searches.
So for example alt text that read ‘womens pink converse shoes’ is more effective than ‘womens shoes’.
And finally, test your images
If you’re unsure whether or not you have included alt text on all the images on your site, try out this handy free tool by Feed The Bot.
Simply enter in a URL and it checks the alt text on any web page. Hey presto!
This article was updated in September 2019.