Make accessibility
part of your everyday.
Check contrast, HTML and PDFs. Keep human judgment in the process.
Color contrast checker
Pick two colors. See how they work together.
Large text is at least 24px, or about 18.7px when bold. Thresholds apply to text contrast, not overall accessibility.
includes everyone.
This is how your colors look in a real sentence. Readability starts with a clear relationship between text and background.
A clearer way forward →What does this result mean?
Contrast measures the difference in luminance between text and background. WCAG 2.2 AA calls for at least 4.5:1 for normal text and 3:1 for large text. Normal-text AAA uses 7:1. Font weight, size, interaction states and the complete design still need review.
Read the W3C contrast guidance ↗Small markup. Meaningful improvements.
Paste HTML or try the example. Checks run in your browser without executing the markup.
HTML snippets only. Use the PDF check tab for documents. Office files, screenshots and live URLs aren’t supported.
Your results
Ready when you are. Run a check to see potential issues and suggested fixes.
Checks cover text alternatives, headings, form labels, control names, link wording and table structure. Full-document input also gets language and title checks.
Why does the improved example still need review?
Markup checks can identify some barriers. A person must still verify whether an image description is useful, links make sense, keyboard interactions work and the complete rendered experience is accessible. No findings in these checks does not mean full conformance.
Is your PDF ready to be read?
Check tags, text and link labels. Then review the reading sequence with a person.
Choose a document
Up to 20 MB and 100 pages. Your PDF is processed in this browser; it is not uploaded to the site or sent to the AI reviewer. The PDF parsing library loads from cdnjs.
Try an example first
These small, fictional PDFs demonstrate the difference between untagged content and a document with a simple tag structure.
Choose a PDF or try a sample.
No document checked yet.
A tag tree is evidence of structure, not proof of logical order or full accessibility. Images, tables, forms, reading order and screen-reader behavior still require manual testing.
What needs attention
Links & calls to action
Labels are read from link tags when they can be matched to annotations. Otherwise, visible text is estimated from the link’s position. Confirm the accessible name and purpose with a screen reader.
Review the reading sequence
This is a text preview of available tags, not a screen-reader simulation. Verify columns, captions, tables, meaningful images and interactive elements in the document’s tag tree and with assistive technology.
Human review & report
Exports a text report, not a remediated PDF. These checks do not certify PDF/UA, WCAG conformance or legal compliance.
What do tags and descriptive links mean?
Tags describe document structure—headings, paragraphs, lists, links and other content—and support reading order. Link text should explain its purpose in context. Tag presence and meaningful link wording must be checked alongside actual reading behavior.
W3C: PDF reading order ↗ · W3C: PDF links ↗A useful second opinion.
Ask about an accessibility finding, wording or a snippet of HTML.
Keep a person in the process.
Resolve findings, check the full experience and keep a record of your review.
Your review checklist
Take your findings with you.
Human review pending.
Run an HTML check to enable this export. PDF reports are available in the PDF check tab. The report includes findings, the color pair, your notes and review acknowledgments. AI chat is separate.