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Alt text is metadata intended to communicate an image’s purpose—not repeating page content. Users of assistive technology rely on alt text to accomplish a task, so usability is key.
As content creators, we often use images that visualize information already communicated elsewhere in writing (for the benefit of recall for sighted users).
But for folks that use screen readers, is redundant alt text truly helpful? Note these considerations:
- Is the task-related information in the image also found elsewhere on the page? If not, then the image is not redundant and requires alt text.
- If yes, does the page copy directly reference the image? If so, it’s important to provide alt text so screen-reader users can find the relevant image and won’t feel they’ve missed something that sighted users can access.
- Could alt text help users more efficiently complete a task? Include redundant alt text for the sake of efficiency only if it will help with users’ most frequent tasks and use cases.
If alt text is needed, here’s how to do it right:
- Keep alt text concise (under 150 characters).
- Avoid words like “image” since screen readers identify images.
- Mention the image type (e.g., chart) only if helpful.
- Start with the most important details to grab attention.
- Avoid technical jargon and abbreviations unless universally understood.
- Always end with a period for screen reader pauses.
- Include alt text for every image, even if it’s empty (alt=””).
- Reevaluate alt text for each placement to match context.
- Provide translations for all supported page languages.
- Mention identity (e.g., race, gender) only if relevant to the image’s purpose.
Take a closer look at NN/g.
