Alternative text, or “alt text” describes the content of images, graphs and charts. It should be added to every image that conveys meaning in instructional and communications materials including word processing documents, and slide presentations.

Impact

There are two groups of people you need to consider when using or creating images in digital content: those who can see them and those who can't. 

It may seem obvious that you'll need to provide the information in an alternative format for people who can't see your visuals—those who are blind or visually impaired. 

Users implementing screen reading software rely on Alt tags and Title tags to convey and images meaning and purpose. 

If you don't include alternative text with an image, a visually impaired person or user who disables image loading or encounters a broken image won't know what the image is meant to convey.

Example

Adding Alternate text (Alt text) in Drupal. 

In the main ul.ie template when adding an image there will be a field to add Alt text .

You may have to add the image first to see the fields.

What to put in an ALT tag and Title Tag of images. 

Alt Tags should describe the image and the purpose of the image with in the context of the page it is on. For more information W3C: images tutorials , for an exhaustive tutorial on Alt tags. 

It is recommended that you do not use "UL" in ALT or title fields. 

A modern screen reader will read UL as UL as in Hull. It is recommended to use University of Limerick or "U.L".  

A handy list of tips and trick for alt tags. and an alt Tag Decision Tree to help you add your alt tag.