In short, alt text is a an attribute that is added to the html of a page to tell the user what is contained in an image. There are various applications of alternative text but the important point to note is that it should be an accurate description of the image.

Note that whilst it is technically the alt attribute, it is commonly referred to as an alt tag.

Does the user see an images’ alt text?

If you were to land on a web page and it displayed properly, the user would not immediately see the alternative text on an image, you would see the image instead. However, there are certain instances in which the alternative attribute (alt text) would be displayed to the user:

  • If the browser cannot render the image, usually due to a slow internet connection
  • If the user has a screen reader – commonly used by blind people
  • If the user has their browser set to text only mode or have disabled images on the browser (usually due to slow internet connection)
  • If the user hovers their icon over the image

Why is Alt Text important for SEO?

A picture says a thousand words….to humans. Unfortunately (or fortunately, depending on on your view of AI) Google is not a human and therefore is limited in its capabilities. In this example, Google cannot ‘read’ images. Some have claimed that Google can read text on an image, but we tend to prefer taking information from the horses’ mouth and in their Webmaster Guidelines they explicitly say that the Google crawler cannot read text in images. This may change as OCR or Optical Character recognition advances, but at the moment they advise using alt text to provide a description of the image, not only for the user but also for Google.

Web design is rapidly moving towards less text heavy sites and more image led ones. As a result, Google is working off less and less information that the crawler can read (i.e text) so the image alt attribute can be used to fill in the gaps of Google’s knowledge, i.e give a description of the image content. Google also recommend that you include some descriptive text in the content around the image as well as the alt attribute.

As is the theme with all of our SEO tips, the alt text of an image should be an accurate description of the image itself. In turn, your images should be an accompanying piece of content to the text on the page (and relevant to the subject). Therefore, it is a good place to add search terms to the page where relevant.

Due to the fact that it is a description of the image, alternative text is a key factor in image search. Whilst SEO is mainly focussed on organic search results, image search is search nonetheless. Including great imagery on your site which then ranks on image search should be viewed as another opportunity to capture your target audience.

The title of the image should also be optimised instead of the jumbled numbers that are probably outputted by your camera or phone. To avoid any potential issues, your title and alt text should be relatively similar.

Technical Implementation of Alt Text

In most CMS’ there will be an alternative text function to each image. In WordPress, simply click on the image once it has been uploaded to the gallery and there will be a box on the right hand side underneath the image title and caption that says Alt Text.

The code for alt text is:

<image src=”” alt=”insert alt text here”/>