The accessibility standard the document claims

Declare the document built to be read aloud and described, and have that claim checked against what it actually carries.

In plain words

Written for anybody. It says what this puts on a sheet of paper, and asks nothing of you beyond that.

Somebody who cannot see the page reads a document through a program that says it aloud. For that to work the file has to carry, beside the ink, what each piece of ink is: this is a heading, this is a paragraph, this is a picture and here is what it shows, this line is decoration and should be skipped. A standard says exactly what a file must carry to be readable that way, and this is where you claim it. The claim is not taken on trust: it is checked against the structure the document says it is made of, the furniture it leaves out, the fonts it carries and its title, and a document that does not hold up is refused rather than shipped saying something false. It is what decides a public-sector contract, where the claim is a requirement rather than a courtesy.

For a developer

Written for somebody who writes the calling program: the model, the units, and the settings that carry the weight.

Written at the top level of a request, under "accessible"

accessible names the accessibility standard the document conforms to. The claim is judged, not recorded: it is checked against the tree the document says it is made of, the furniture it leaves out of that tree, the fonts it carries and its title. The part chosen also fixes the version of PDF the file is written as, and no other — PDF/UA-1 is built on PDF 1.7, PDF/UA-2 on PDF 2.0, whose tree is rooted in one Document element named from the PDF 2.0 set of tags. It goes hand in hand with structure, which is what the check reads, and it stands beside archive rather than replacing it: a document may be both archival and accessible.

Every key, with its default

The reference: which keys are required, which are optional, what each one defaults to and which combinations the server declines.

  • accessible — string, optional. Absent, the document claims nothing.
  • pdfua1 — ISO 14289-1, the part built on PDF 1.7. The file is written as PDF 1.7.
  • pdfua2 — ISO 14289-2, the part built on PDF 2.0, whose tree is rooted in one Document element named from the PDF 2.0 set of tags. The file is written as PDF 2.0.

Scope: the whole document. It fixes the version the file is written as, so it is refused beside a version that says otherwise. A document claiming a part it does not hold up to is refused when the request is read, not shipped with a claim that is false.

A whole request that draws it

Post this as it stands and a PDF comes back. Nothing has been left out of it.

One name below stands for a font file: put the encoded file in its place, or send the file itself beside the description, as a part of the same call.

{
  "accessible": "pdfua1",
  "metadata": { "title": "A readable document" },
  "fonts": [{ "name": "body", "data": "PASTE_THE_FONT_FILE_BASE64_HERE" }],
  "structure": {
    "lang": "en-GB",
    "children": [
      {
        "tag": "Document",
        "children": [{ "tag": "H1", "content": "heading" }]
      }
    ]
  },
  "items": [
    {
      "type": "text",
      "rect": { "llx": 72, "lly": 700, "urx": 523, "ury": 740 },
      "content": ["A readable heading"],
      "font": "body",
      "font_size": 20,
      "tag": "H1",
      "mark": "heading"
    }
  ]
}

The line that sends it, in three languages

The document as a whole

The numbers the reader shows A hundred letters in a single file What the document says about itself A file still readable in thirty years An invoice a person and a machine both read The address relative links are read against The PDF version the file declares What an image says about itself Files the document carries beside its pages Which carried files a page claims The identity card a single page carries

Where to go next

Every key of a request, in one page The other thirty-two settings of a request

See the prices See the examples

Glossary

standard
A rule argued out in committee, published under a number anybody may buy and read, and identical for every firm claiming it. A claim to follow one can therefore be checked against the text. A way of working that merely spread because it worked is a habit of the trade: useful, widespread, and answerable to no text at all.
PDF/UA
A PDF a blind reader can use. The file itself says which text is a heading, which is a paragraph, and in what order the software that reads a page aloud should say it all. Without that, the software reads the page in the order it was drawn, which is rarely the right one.
CMYK
The four inks a printing press lays down: cyan, magenta, yellow and black. A screen mixes light instead, so a document going to a press states its colours in inks, not in screen colours.
font
The drawing of every letter, digit and mark a document writes, held in a file of its own. A PDF carries the fonts it is set in inside itself, which is why it opens looking the same on a machine that has never had them. Leave them out and a reader puts another font in their place, and the layout moves.
tagged PDF
A PDF that carries the structure of its own text alongside the drawing: this is a heading, this is a table, this cell belongs to that column. It is what lets a reading aid, or a program pulling data back out, make sense of the page.
request
One call to the service: you send what the document should say, and get the document back. Your bill counts these calls, one for each document. The number of pages inside a document is never counted.

Every word the site explains