All images relevant to the course content will need alternative (‘alt’) text and potentially long descriptions so that any of your learners relying on a screen reader will be able to find out what is included in the image.

It is also helpful for when images cannot be loaded due to data or bandwidth restrictions.

Alt text should typically be up to 750 characters (including spaces). How much detail you go into depends on what your learners need to know. If you're showing them a graph to show how a trend increases steadily over time, you only need to say that. If it's important that your learners know a percentage for each year, for example, then you need to include that detail. Any text should be written word-for-word and any data should be described fully.

Note that decorative images – that is, images that do not have any learning benefit – do not need alt text.