What is Alt Text or “Alt Tags”
Alt text (or as they are colloquially known Alt Tags) are small pieces of text description that are associated with images in html and explain what a specific image on a website depicts.
<img src="image.jpg" alt="this is alt text" />
They were originally created to make the web more accessible, by describing images to those who cannot see them. This includes people using browsers that don’t allow images but primarily sight impaired people who are using screen readers to convert a website’s content into audio or braille.
Why is Alt Text important in SEO
There is still little evidence to suggest that Google uses any form of image processing to infer what an image might be about. Instead Google is still heavily reliant on the content of alt text to understand what the images on a website are about.
As a result it is important that we provide this information in alt text so that images that might be providing a user with important information on a website are understood better by Google.
Keep it readable. While alt text does provide us with an opportunity to inform Google about what our page is about, it is important that alt text is readable. We should not be stuffing keyword terms into alt text in a garbled, senseless way. Fundamentally the alt text should accurately describe what the image it is associated is of.
Keep it quite short. Most screen readers will only process the first 125 characters of your alt text. You can have a longer alt text than this but don’t go mad.
Try to take into account your keywords. While I am not condoning stuffing keywords into the alt text it is worth taking into account the sorts of keywords we are aiming for the page the image appears on to rank for. We may not include these phrases but we might include related terms or synonyms if they are relevant to the content of the image. So for example if we have an image of someone riding a Gocycle G4 and we want our page to rank for the phrase Gocycle G4 electric bike, we might use the alt text “A Gocycle G4 electric bike being ridden in the UK”.
Alt Text and WordPress
If we were editing the HTML directly we would have to set the alt text for images individually on every page. However on WordPress by changing the alternative text field in the WordPress media library for an image it will update on every page that it appears on. This makes changing alt text on your site less time consuming. However be aware that this will mean that the alt text has to work well for a variety of different pages, for example category and individual product or blog pages. It would therefore be prudent to include keywords for both in some images. In other words to think about the categories the image will appear on as well as the individual post pages.