What is alternative text (alt text)?

What is alternative text (alt text)?

Introduction

‘Alternative text’ (alt text) is 1 or 2 sentences of written text which describe an image in context. Alt text is helpful for anyone using a screen reader to access your content.

Screen readers are a type of assistive technology. They are used by many disabled people, including people who are blind and people with sight loss to make digital documents accessible. Many non-disabled also use screen readers as a productivity tool.

Screen readers read out text, but cannot read out images. This means that a screen reader user will miss your image, unless you create alt text to describe it to them.

Most programs give you the option to add alt text to your images. If you are creating a Word document in Office 365, for example, right clicking on an image within the document will bring up the option.

How to write alternative text: Top Tips

Describing an image in just a couple of sentences can be a challenge, but it is really important in terms of making your document accessible. Here are some tips to help you:

• Alt text should be no longer than 1 or 2 sentences. If you are using a complex image then a text transcript may be a better alternative. Infographics and tables are two examples of more complex images. Our resource, ‘How to use images in an accessible and inclusive way’ provides more information on writing text transcripts.
• Write alt text using plain English.
• Alt text should be descriptive and specific. Think about the purpose of the image in your content and the message you are trying to express. Only include information in the alt text which is not included in text elsewhere in the document, such as in the copy or in captions.
• Alt text should be in context. You might use the same image in several documents on different subjects. Make sure your alt text gives the image context in this particular document.
• Don’t waste words. You don’t need to say ‘image of’ in your alt text. Screen readers will tell the user that it is an image.
• Some programs may suggest alt text for you to use. Always check this for accuracy and meaning before using it.
• Decorative images do not need alt text but must be marked as decorative, otherwise screen readers will read them as a blank. To mark an image as decorative, add two quotation marks like this “” in the alt text box. Some programs also give you a ‘mark as decorative’ option.
• Decorative images include logos, headers, any images which are already described in the surrounding text, and images that are for visual effect only.
• If in doubt, provide alt text.

Example photo with and without alt text

An image may need alt text if used in one way, but may not need alt text if used in a different context. As the author, you need to decide what purpose the image is serving.

If the above image of a man smiling and holding a phone was being used as a generic illustration in a resource which talks about your telephone advice service, then alt text would not be needed. The image is just for visual effect.

If, however, you used the image in the same context but with the header, ‘Meet our advice service’ then alt text should be provided to describe the visual appearance of the team member for anyone who cannot see the image. This could be ‘Steve wears glasses and has facial hair’ and it could be used along with a caption which reads ‘Steve is our Advice Service Manager’. The alt text provides additional information not provided in the caption or in any other text.

Your alt text would need to be different if the same image was being used for another purpose. For example, if the image was being used on your website to promote a new range of glasses, with the simple header, ‘Take a look at our new range’, alt text for this image could be:

‘Male wearing rectangular shaped glasses with black plastic frames.’