Taggart
PDF/UA checker: free PDF accessibility checker online
A free PDF accessibility checker online: any PDF against the Matterhorn Protocol, PDF/UA-1 and WCAG 2.1 AA. No watermark; no account up to 60 pages.
What it checks
The machine-checkable failure conditions in the Matterhorn Protocol 1.1, the PDF Association’s conformance testing model for PDF/UA-1: 31 checkpoints covering tagging, role mapping, metadata, character mappings, natural language, graphics, headings, tables, lists, notes, optional content, security, annotations, XObjects and fonts.
A few of them, all about the insides of embedded font programs, Taggart does not check yet. They are not quietly passed: every report lists them as conditions to confirm before a conformance claim, and each one’s page says so.
Each finding is mapped to its PDF/UA-1 clause and, where one applies, its WCAG 2.1 success criterion — so one check answers both questions.
Three profiles:
- PDF/UA-1 (ISO 14289-1) — every condition Taggart checks
- WCAG 2.1 Level AA — only conditions with a mapped success criterion
- IS 5568 — the WCAG-mapped set plus Taggart’s right-to-left conditions
Plus three things a conformance checker does not normally give you: a screen-reader preview showing exactly what is announced and in what order, a right-to-left analysis that detects visual-order Hebrew and Arabic, and a structure tree with per-element geometry.
What the severities mean
Findings are not a flat list, because the conditions are not equivalent.
Blocker — a machine-checkable PDF/UA-1 requirement is failed. Definite; the file cannot claim conformance until it is resolved.
Warning — the condition either has no machine test or passes one, but a heuristic says a human will reject it. A table with no header cells, a run of paragraphs that is obviously a list, a running head sitting in the reading order.
Needs a decision — genuine judgement. Taggart presents the evidence and records what you decide. It never auto-passes these, and it never fails them on a guess either.
What a checker cannot decide
The Matterhorn Protocol is explicit: of its 136 failure conditions, 87 can be decided by software, 47 require human judgement, and 2 have no specific test at all.
That ratio is the honest answer to “is my document accessible”. A clean checker run means the machine-decidable third is right. The rest — whether the alt text is true, whether the order is the author’s intent, whether that grid is a table — needs a person, and any tool reporting a compliance percentage is reporting the percentage of what it can see.
Using it
Drop a PDF in. Results in about a second for a typical document. Nothing to install.
Every finding carries a plain-language explanation, a line describing what a screen reader actually does when it hits the condition, the Matterhorn ID, the PDF/UA-1 clause, the WCAG criterion, and the page and structure path of every occurrence.
Several files at once work too. Drop a batch in and the app checks them two at a time into one table — pages, blockers and warnings for each, and how many have nothing wrong — and any one of them opens into the full view. That is where triaging a backlog starts.
Check a PDF free → · Browse every failure condition →
Frequently asked questions
Is it really free, or is there a catch?
Free, unlimited and not a trial. It checks most of the Matterhorn conditions software can decide and lists the few it does not check yet for a person to confirm; no watermark, no expiry, and no page cap once you have a free account — signed out it stops at 60 pages. Checking is commoditised — PAC, veraPDF and PDFix Lite all do it for nothing — so charging for it would only send you to one of them. Remediation is what a plan pays for.
How does it compare with PAC?
Both test the machine-checkable Matterhorn conditions, though Taggart does not yet check a few of the font ones, and we have not yet cross-checked the two against each other. PAC is Windows-only and fixes nothing; Taggart runs anywhere and can also repair. Run both — two independent implementations agreeing is worth more than either alone, and where they disagree, read both findings and tell us.
What can a checker not tell me?
Roughly a third of what matters. Whether alt text is accurate, whether the reading order matches the author's intent, whether a heading is a heading, whether a table is data or layout — all judgement. The Matterhorn Protocol itself says 47 of its 136 failure conditions require human judgement, and two have no test at all.
Do you store my document?
A signed-out check is processed and discarded — nothing is stored. Signed in, a check of your own file is kept in your History for seven days, then deleted along with any repaired file made from it; you can delete it sooner.
Related guides
- How to check if a PDF is accessible: four free checkersCheck PDF accessibility free, online or on your own machine: four checkers against PDF/UA and WCAG, what each catches, and the failures none of them see.
- Acrobat accessibility checker: every rule explainedWhat each of the 32 rules in Acrobat's Full Check means, which PDF/UA condition it matches, and how to fix it — from Tab order failed to Logical Reading Order.
- A PDF accessibility checklist that is honest about limitsTwenty-two items in the order they should be done, each marked as machine-checkable or human judgement, with the Matterhorn condition behind it.
- PDF/UA vs WCAG: which one applies to your documentsOne is a format standard a validator can test. The other is what your legal obligation cites. They overlap heavily and neither one contains the other.
Run your own file through it. The validator is free and unlimited — no page cap, no watermark, and no account at all up to 60 pages — so you can see exactly what you are dealing with before deciding anything.
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