Usability and accessibility » Alt texts

Sebastian Greger This is a living document
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So called alt-texts (alternative text) are the default means to make visual content accessible in a descriptive format. But using them correctly is not an easy, and for sure not precise, science.

For a first deep dive, this text aims to summarize all the most important aspects:

Comprehensive summary of “everything you need to know about alt-texts”

Decision trees

Decision trees are intended to help decide whether and what kind of alt text to use.

The WAI’s decision tree is based on the content of an image

A decision tree based on the purpose and role of the image to be described; see subheading “What is the best way to add alternative content to images?”

Content design considerations

Writing alt texts is not an easy task, but a key part of the design process. Creating good text descriptions for images is an art of its own, but not one that couldn’t be acquired.

Hints for creating alt texts that convey not just the content but the spirit of an image

A perspective on why race and gender should have a place in alt texts as well

Also the appropriate length of an alt text is a debated aspect:

Making SVGs accessible

Things work slightly differently if SVG vector graphics are embedded directly (not as an <img>).

AI to the rescue?

Recently, one may occasionally see suggestions to use AI technology to compensate for a lack of alt texts, or to simply make writing them obsolete.

Browsers may offer their users to send images without alt texts to an ML-based software to provide an interpretation.

Alt texts in HTML email

The same rules apply for HTML used in email as well. With their generic browsing engines, there are however a long range of aspects to be considered.

Getting alt texts right in email is not easy, not least because of inconsistencies between software clients.