Accessibility · official-source review · reviewed 2026-10-10
Most alt text is either too short to be useful or too long to read, because there is no length target for the image's job.
Give a recommended alt-text character count based on whether the image is decorative, informative, a chart, or a control.
Writers and web builders writing accessible alt text.
Use the source document or official route that applies to your situation. This guide does not contact another person or verify external information.
Classify the image: decorative, informative, chart/graph, or functional control.
Use the appropriate character count for the job.
Describe what the image communicates in that length, not every visual detail.
Read it aloud; if it sounds tedious, it is too long.
A bar chart showing quarterly sales should get 125–250 characters describing the trend and key values, not the word 'chart'.
Use your own source and details. The example is not a record about a real person or organization.
W3C Web Accessibility Initiative · reviewed 2026-10-10
What this source supports: Alt text length and content depend on the image purpose: decorative images get empty alt; informative images carry the purpose in a concise sentence; charts describe trend and key data.
Source limit: This tool gives length guidance; actual alt text must be written to the specific image.
These sources support the statements above. They do not show that every person needs this guide. They do not show a specific result.
This App recommends a length and structure. It does not write alt text for you.
This tool gives length guidance; actual alt text must be written to the specific image.
Use current instructions from the responsible organization. This guide is a planning aid, not an official decision or a substitute for qualified advice.
Recommend alt text length and structure based on the image's job.
This gives guidance. It does not generate alt text or evaluate your writing.
You enter every number yourself. The sources support the method and the limits. They do not produce a result for your specific case. Keep the original documents next to the sheet you build.
The App computes the worked example with your own numbers, in your browser.
APP 1
Recommend alt text length and structure based on the image's job.
Free · no account · no upload
Open Alt Text Length PlannerThe App runs in this browser. It does not send or save entries. Copy, download, or print only when you choose.
This guide uses short, direct instructions as an ASD-STE100-style writing target. It is not a formal certification.
Companion App: Alt Text Length Planner. It runs in this browser and does not upload your entries.
This guide is edited for clarity and checked against the sources it links. It is not a substitute for official instructions or qualified advice. A linked source does not show that every person needs this guide.