Alternative text (alt-text) provides a text alternative to non-text content (mainly images) on web pages or in files. Alt-text is useful because it can be read by screen readers to make images accessible to people with visual or cognitive impairments, it can be displayed in browsers if an image does not load properly, and it provides a meaningful description of images that can be read by search engines. Keep the following in mind when writing alt text for images:
- Be accurate and equivalent.
- Be succinct and not redundant.
- Do not use the phrases “image of …” or “graphic of …” to describe the image.
How to Write Alt Text for Complex Images
Complex images convey more information than normal images do, and they cannot be explained in a short phrase or sentence. Complex images typically include graphs and charts (like flow charts and organizational charts), diagrams and illustrations, and maps showing locations or other information (like weather systems). In these cases, it is best practice to include a short alt text of the image and indicate where to find the long description of the image. This could include:
- Putting a link to the long description near the image, or
- Describing where the long description is in the alt attribute.