Good alt text

When writing alt text, you must ensure it is:​

• Informative – It provides useful, accurate information on the visual information contained in the image, in a coherent manner, as a sentence if possible.​

• Descriptive – Good alt text describes what is happening in the image, and the purpose of the image. ​
  
• Concise – not longer than 150 characters, you do not need to describe every last detail of the image, just the key elements. You do not need to start your alt text with ‘a photo of’.​
  
• Relevant – the context of the image and where it is placed within the text content is important. 
  For example, for an image of the Mona Lisa, it may not be necessary to include details such as ‘Renaissance oil painting of a person with an ambiguous smile’. ‘The Mona Lisa’ may be more appropriate alt text, if the purpose of the image is to give an example of a famous painting.​