Accessibility · official-source review · reviewed 2026-10-09
Alt text fails in both directions: one-word labels that say nothing, and paragraphs that should have been a caption.
Classify an image as decorative, functional, or informative, then check the alt draft's length and content.
Authors and editors writing alt text for real pages.
Use the source document or official route that applies to your situation. This guide does not contact another person or verify external information.
Use the WAI decision tree to classify the image first.
Draft alt text that matches the class you chose.
Check the draft against a 125-character working band.
Test the final page with a screen reader once.
An informative image alt of 118 characters passes the length band and keeps the key noun in front.
Use your own source and details. The example is not a record about a real person or organization.
World Wide Web Consortium, Web Accessibility Initiative · reviewed 2026-10-09
What this source supports: WAI's decision tree asks authors to decide whether an image is decorative, functional, or informative before writing alt text.
Source limit: Context changes the right alt text. Test with a screen reader for your own page.
These sources support the statements above. They do not show that every person needs this guide. They do not show a specific result.
This guide checks drafts you enter. It does not audit whole sites, generate text with a model, or test with a screen reader for you.
Context changes the right alt text. Test with a screen reader for your own page.
Use current instructions from the responsible organization. This guide is a planning aid, not an official decision or a substitute for qualified advice.
Measure an alt draft's character count against a working band and flag missing descriptive shape.
This App measures the text you enter. It does not judge meaning for your context, generate alt text, or run a screen reader.
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
Measure an alt draft's character count against a working band and flag missing descriptive shape.
Free · no account · no upload
Open Alt Text Length CheckerThe 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 Checker. 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.