Skip to content
SilktideHelp

PDF content tagging

Silktide checks that every mark on a PDF page is accounted for: either tagged as real content, or flagged as decoration that should be skipped. This check also reports the two being nested inside each other, where real content sits inside a decorative region or the reverse.

An accessible PDF has no third category. Content belongs in the where can find it, or it is marked as an and deliberately hidden. Anything that is neither has no defined status, and readers disagree about what to do with it.

Why this matters

Content that falls through this gap disappears. A pull quote, a caption, a figure of a chart, an entire sidebar can sit plainly visible on the page and simply not exist for someone using a . Nothing announces the omission, so the reader has no way to know that part of the document was withheld from them - which is worse than a document that is obviously unusable, because it feels complete.

Nesting causes the mirror image of the problem. Meaningful content placed inside an artifact is skipped along with the artifact, because hiding is the whole purpose of an artifact and readers do not look inside one. Decoration nested inside tagged content is announced as though it mattered, which is how a reader ends up hearing a page number in the middle of a sentence, or a decorative rule read out as a stray character.

This check is also why a document can be tagged and still be unreliable. Tagging some of the content is not a partial success; the untagged remainder is invisible.

How to fix it

  1. Tag anything that carries meaning so it joins the structure tree: text, tables, and any figure a reader would ask about.
  2. Mark decoration as an artifact, and mark it fully. Background images, page borders, decorative rules, watermarks, and running headers and footers all belong here. See Hidden decoration for what Silktide treats as decorative.
  3. Move anything meaningful out of an artifact. If a graphic contains the only copy of a fact, it is content, however decorative it looks.
  4. Re-export from a workflow that does this for you. Tools with a PDF/UA export path account for every mark automatically, which is far more reliable than sweeping a finished file for gaps.
  5. Or run Silktide remediation, which tags real content and marks decoration as it rebuilds the structure. See How PDF remediation works.

How Silktide tests this

  1. Find the PDF documents linked from your website, and analyse each unique file once however many pages link to it.
  2. Walk the page content looking for marks that are neither tagged into the structure tree nor marked as artifacts.
  3. Check whether tagged content appears inside an artifact, or an artifact inside tagged content.
  4. Report the document when any of those apply, once per document however many places are affected.

Untagged documents are reported by PDF tagging instead. This check is about the gaps in a document that does have tags.

Troubleshooting

Nothing looks missing when I read the document

That is the expected experience. Whether a mark is tagged makes no difference to how the page is drawn, so this problem is invisible unless you inspect the tags or use a screen reader. Silktide's screen reader preview shows the document as assistive technology receives it, which is the quickest way to see what is being dropped.

The affected content really is decorative

Then mark it as an artifact, and the check is satisfied. Decoration is not a problem in a PDF - undeclared decoration is. The standard asks you to state which it is rather than leave a reader to guess.

My headers and footers are reported

Running headers, footers, and page numbers should be artifacts, and specifically pagination artifacts. Repeating them as real content on every page is its own accessibility problem, because a reader hears them between every section. See Headers and footers.

Learn more

Last updated

Was this page helpful?