A replacement counts when four things are true at the same time. It conforms at the level you are claiming. It carries all of the same information and functionality, in the same language. It is as up to date as the PDF. And somebody meeting the PDF can find their way to it. Miss any one and you have two documents rather than one document with an alternative, and the non-conforming one is still sitting inside your scope.
The one that fails in practice is the third, and it fails quietly. Everything else is checked on the day the page goes live, when the two versions genuinely do match. Currency is the condition that has to keep being true, and nothing in the publishing process notices when it stops.
The Four Conditions, and They Are Joined by And
| Condition | What it means in practice | How it fails |
|---|---|---|
| Conforms at the designated level | The replacement itself meets the level you claim, in full. It is not enough for it to be better than the PDF | The HTML page inherits the site template's own failures and nobody audited it separately |
| Same information and functionality, same language | Everything the file said, and everything the file let somebody do. A fillable form's alternative has to be fillable | A summary. A table dropped because it was hard to mark up. A form turned into a phone number |
| As up to date as the non-conforming content | When the PDF is revised, the page is revised. Version four of the file next to version two of the page is a failed condition, not a small lag | Nobody owns the pairing, so the file gets updated through the normal process and the page does not |
| Reachable, by one of three routes | A link from the file or the page holding it, or a route where the PDF can only be reached through the accessible version | The page exists and nothing points at it, which has its own named failure |
Two things the conditions do not ask for are worth saying out loud, because teams over-build against imagined requirements. The alternative does not have to match page for page, and it can be several pages where the file was one. And it does not have to live on the same website, as long as it is as freely available as the file it replaces. So the shape is genuinely yours to choose. The content, the function, the currency and the route are not.
The Third Condition Is the One That Rots
Think about what happens after the launch. The PDF is the thing your organization already knows how to produce, so the next revision goes through the same route it always did. Somebody edits the source, exports a new file, uploads it over the old one. The HTML page was a project, and projects end.
Six months later the file says one thing and the page says another, and the equivalence that was real in March is not real now. Nobody made a decision to break it. That is what makes it worth designing against rather than checking for, and the design is simple enough. The pairing needs an owner, and updating the page has to sit inside the same process that updates the file rather than beside it.
So put the last-reviewed date on both, visibly, and make them match. It is a small thing and it turns an invisible condition into something anybody can check in four seconds, including the reader who is trying to work out which version to trust.
Findability Has a Named Failure of Its Own
The route condition is the one with the most published detail behind it, and there are three ways to satisfy it. Link from the non-conforming version to the conforming one. Arrange things so the PDF can only be reached from the accessible version. Or arrange things so the PDF can only be reached from a conforming page that also offers the accessible route.
Most sites want the first, and there are two published techniques for it. A link at the top of the non-conforming page covers the case where the reader has landed on the document itself. A link next to the non-conforming object covers the far more common case on a website, where the PDF is a download sitting on a page you control, and the accessible route goes beside the download link where somebody will actually meet it.
The other two routes are server work rather than content work, using an .htaccess rule or a referer check to make the accessible version the only door. They are stronger and less common, and they are the right answer when the file is also reachable directly from search results.
Getting this wrong has its own name in the standard's failure list. Not providing a way to find the conforming version is a documented failure of the first conformance requirement, which means the alternative you built does not count and the page it was meant to rescue is still non-conforming. An accessible version nobody can find is the same as no accessible version at all.
Functionality Is Half the Condition and Gets Half the Attention
The condition says information and functionality, and the second word is where most replacements quietly fall short. A PDF that is only read is easy to replace with a page. A PDF somebody has to do something with is a different job.
- A form to fill in. The alternative has to be completable, and by preference as a real web form rather than as a page telling somebody to print it. A printable page is not equivalent to a fillable file.
- A form to submit. If the file could be filled and returned, the alternative needs a route that ends in the same place, with the same receipt.
- A document to search. A long report gets searched. If the page splits it into 40 sections with no search, somebody lost a function they had.
- A table to read across. Tables are the most common thing dropped in a conversion, usually because marking one up properly takes longer than typing prose. A dropped table is dropped information.
- Figures and charts. These need the same treatment they would need anywhere, which is a text alternative that carries the finding rather than a description of the picture.
What W3C Thinks of the Pattern, Which Is Worth Knowing
The alternate version provision exists and it is grudging, and reading it that way helps you use it well. The guidance calls providing an alternate version a fallback, and says plainly that the preferred method of conformance is to make all content directly accessible. It also requires that authors relying on one make users aware that it exists, which is the route condition restated as a duty rather than a technique.
There is a passage about legacy documents that reads like it was written after a long meeting, and it describes a lot of organizations exactly. Bodies that have adapted to publishing on the web while keeping a paper mindset, insisting on print-oriented formats as the primary version even for documents that only ever exist electronically. The working group's own words are that it feels these approaches should be deprecated, and does not feel they can be forbidden so long as accessible versions are readily available.
So the provision is a permission rather than an endorsement. If you are choosing between repairing the file and building the page, the standard has a preference and it is not the page. If the file genuinely has to stay, because the layout is the content or somebody has to sign it, then the four conditions are how you make the page count.
The Comparison Sheet
Run this once per pair, and keep it with the pair rather than in the audit report, because it is a maintenance artifact more than an audit one. Seven lines and you will know in twenty minutes whether the replacement holds.
- Content, section by section. Walk the file's headings against the page's and mark anything missing in either direction. Extra content on the page is fine. Missing content is a failed condition.
- Tables and figures. Count them in the file. Find them in the page. This is where the losses are.
- Functional actions. List what a reader can do with the file, then do each one on the page.
- Language. The alternative has to be in the same human language, and where you publish in several, each language needs its own alternative.
- Dates. Last revised on the file, last revised on the page. Write both down. If they differ, the third condition has already failed.
- The route. Stand on the page holding the PDF and find the accessible version without knowing it exists. Then try it from the file itself.
- Findings on the page itself. Audit the replacement as a page in its own right, because a conforming alternate version has to actually conform, and an alternative that fails at Level AA rescues nothing.
Line seven is the one people skip, and it is the one that turns the whole exercise into box-ticking when it goes unchecked. The alternative is not exempt from the standard because it is an alternative. It is the version carrying the conformance claim, so it gets the harder look, not the easier one.
What This Review Does Not Settle
An equivalence review is a technical comparison against a definition in the standard. It tells you whether the page counts as a conforming alternate version. It does not tell you whether a regulator, a court or a procurement team in your jurisdiction will accept that arrangement, because those are legal and commercial questions with their own answers in each place, and the definition is not a defense that travels on its own.
It also does not decide the cheaper route for you. Sometimes repairing the file is a morning and the page is a fortnight. Sometimes the file is a scanned brochure that was never a document, and the page is the only sane answer. Work out which one you are holding first, and what makes a PDF readable is where that comparison starts.
One honest limit
We audit and never repair, so an equivalence review hands you the comparison and the findings rather than a quote for writing the page. Every example above is illustrative rather than a real client's document pair. If you have a pair you want checked, describe it through contact, and if what you actually need is the file itself looked at, that is the PDF accessibility audit.