Any visual content that has a purpose beyond being purely decorative should have a text alternative for those who can't see it. 

Often there's an alternative text (alt text) feature build into editing tools such as Word, web editing software and blogs services such as Wordpress.

Alt text is needed for any image that conveys useful information not available any other way in the content. 

So how do you decide whether it's needed, and what do you write? Writing good useful alt text is subjective, but these pointers will help.

• Close your eyes, and ask someone to read your suggested alt text to you. If you find the description useful and it helps you imagine a reasonably accurate version of the image, you're on the right track
• More alt text advice with examples (Moz.com)
• Interactive training tool about writing good alt text
• codemantra guidance for writing alternative text

Images can sometimes be marked as decorative if they're purely cosmetic and therefore don't convey key information on their own. They can then be happily ignored by screen reader software. 

• Microsoft Word will let you do this. Depending on your version of Word, you can either tick a 'decorative' box, or enter two speech marks "" in the alt text field. Right click on the image to see your options.
• If the image is on a web page, you can enter two speech marks "" into the alt text field to mark it as decorative.

Why this is useful: 

• it would be unnecessary to describe a campus image on the front cover of a handout about learning resources, as it adds no value if you can't see it
• if it isn't marked as decorative and the alt text is left blank, the software is likely to read out the filename, which really isn't useful to the person listening.

If you have to share a resource that contains images with text embedded, the text must be provided in another format that can be selected.

Replace automatically populated alt text

If the alt text field has been populated automatically, this will often be useless information such as the filename. Replace this with something useful!

What should alt text say? Read these tips

How to add alt text

To add 'Alt text' to an image, you can usually right-click on the image to view the options. This should work in most software.

• Microsoft Alt text advice for Word (Office 365) 
• Google - make your document or presentation more accessible
• LibreOffice guidance on creating image descriptions

Most socials have an accessibility option with alt text for posts, and/or caption field.

• If not, describe the image in the post itself
• Write in full any essential text embedded in the image