Writing good alt text

How you write alt text will depend on where the image is located - for example, if it’s on a web page, in an email campaign or on a social media post.

The same image can have different meanings or functions depending on where it is found.

Your goal is to convey in words the information the user might only gain visually.

Alt text should sum up what’s most important for the user to know in the given scenario. It does not need to describe an image in every detail.

Make time for alt text

Writing good alt text can take time and should be built into the content design process.

For website content, you may need input from a subject matter expert (SME) to make sure the image and the alt text are factually correct. This may not be needed for all images but should be factored into your timeline.

Context

To write good alt text consider the context of the image and all the other content that surrounds it before writing.

Think about:

• what is the purpose of the image
• the additional written content it is supporting
• which details are important for the user to know

The more information in the surrounding text, the less alt text is required. Do not repeat what is already on the page as screen readers will read this out.

Ask yourself:

• what information does the image give that the surrounding text in the content does not?
• how would you describe the image to someone on the phone so they could understand what it represents?

Keep it short

Keep alt text short. Ideally, it should be less than 125 characters including spaces. Many screen readers need to scroll the text if it is longer than this so it isn’t a great user experience.