Question 1

What does the PDF Accessibility Checker do?

Accepted Answer

It loads your PDF in the browser using pdf-lib and runs 10+ accessibility checks across the document catalog and each page's resources: document title, language, structure tree (PDF/UA), image alt text, form field labels, reading order, color contrast, bookmarks, tab order, and metadata. It then compares the results against WCAG 2.1 AA, WCAG 2.1 AAA, PDF/UA-1, and Section 508, computing a compliance percentage for each standard, a list of critical must-fix issues, and best-practice recommendations.

Question 2

What extra features does this tool have compared to others?

Accepted Answer

(1) Page-range parser (reuse shared module). (2) 5 accessibility standards (WCAG 2.1 AA, WCAG 2.1 AAA, PDF/UA-1, Section 508, all). (3) 3 check levels (errors-only, errors-and-warnings, full). (4) 10+ accessibility checks (title, language, tags, alt text, form labels, reading order, color contrast, bookmarks, tab order, metadata). (5) Color contrast analyzer (WCAG ratio). (6) Compliance level calculator (% passed per standard). (7) Standard comparator (which standard most/least met). (8) Multi-format renderers (text/HTML/CSV/JSON). (9) Copy + Download. (10) History (localStorage, last 20). (11) Shareable URL. (12) Summary stats (total checks, passed, failed, warnings, compliance %). (13) Critical issue list (must-fix before publish). (14) Recommendation generator (best-practice suggestions). (15) Page-by-page issue count. (16) Severity tagging (error/warning/info). (17) Category grouping. (18) WCAG success-criteria mapping.

Question 3

How does the color contrast check work?

Accepted Answer

The checker scans each page's content stream for fill-color operators (rg, k, g, sc, scn) and text-showing operators (Tj, TJ, ', "). When it can pair a fill color with adjacent text, it computes the WCAG contrast ratio between the text color and the nearest background fill. Ratios below 4.5:1 are flagged as errors for AA compliance; ratios below 7:1 are flagged as warnings for AAA compliance. The check is heuristic — it cannot follow z-order, transparency, or inherited colors — so results should be treated as a triage list, not a substitute for a screen-reader test.

Question 4

What's the difference between 'errors-only', 'errors-and-warnings', and 'full' levels?

Accepted Answer

'errors-only' shows only failures that block compliance (missing title, missing language, untagged PDF, missing alt text on informative images, contrast below 4.5:1). 'errors-and-warnings' adds warnings about issues that may not block compliance but reduce usability (low-contrast text passing AA but failing AAA, missing bookmarks in long documents, missing form-field tooltips). 'full' adds informational notes and best-practice recommendations.

Question 5

Is my data sent anywhere?

Accepted Answer

No. All accessibility checks run 100% in your browser using JavaScript and pdf-lib. Your PDF never leaves your device, and the tool works offline. History is stored in localStorage on this device only.

PDF Accessibility Checker

How to use