What is alternative text?

The purpose of alternative text (also know as alt text) is to provide an alternative for users who cannot see images. This could be because they had a text only Web browser (like Lynx), had images turned off (usually due to slow Internet connections) or could not see the image due to a visual impairment. All images must have alternative text.

Although I’ve already said that alternative text describes an image, that isn’t actually correct. Alternative text should describe the purpose of an image, which is subtly different.

Take the image on the right. If you were describing the image you may say something like:

Four individual type block letters together, forming the word news

If you describing the purpose of the image, you may just say

News

Depending on how you are using the image will affect what you use as the alternative text. For example take the photo on the left, in a general page about Robin Hood it may simply read:

Robin Hood

On the other hand in a page about Robin’s adventures it might read:

Robin aims his bow towards Nottingham Castle

While in a tourism page about Nottingham, it could be:

Bronze statue of Robin Hood, outside Nottingham Castle

Sometimes images are purely used for decoration and don’t really provide any useful information. In that case we still need to tell the image that the alternative text is empty, this means that text only browsers and screen readers (used by visually impaired people) can ignore the image.

So what does all this have to do with SEO?

Now we know what alternative text is, how can we use it in SEO? We can use the alternative text of images as another way of highlighting the key words and phrases for our page. Don’t just stuff key words into your alternative text, but make sure that along with helping people to understand the page it can help people to find it.

Looking at our Robin Hood examples above, they help people to understand the image purpose while giving information to search engines. The final example gives several different key phrases that we might want in a Nottingham tourism page.

Not only does it help our standard search but it means that your page can be found in image searches. If a standard search finds enough images it will often display images there too, making your page stand out more.

Making sure you add good alternative text is really important if you are selling online as people often search for specific items. Making sure your images have good alternative text with key words or phrases that people are searching for will help your product pages rise to the top of search results.