Checking tag-structure of InDesign files

Preisanhänger als Sinnbild für Tags

When working on accessible documents, the free PlugIn “pdfGoHTMLfrom Callas Software is an important helper. Recently, an update was released that removed an annoying bug – namely, the regular crash of Adobe Acrobat when closing the app if the PlugIn was installed.

What can the PlugIn do?

pdfGoHTML shows you the semantic structure of your PDF document based on specified tags. To do this, pdfGoHTML opens your PDF document in your default browser. For an accessible document, it is important to assign these tags correctly. This enables assistive technologies – such as screen readers – to render the content correctly for its users.

Look at the following simple example. It consists only of an image, a heading, a subheading, and body text, some of which is also a bulleted list.

Einfacher Dokument-Aufbau mit Bild und Text

If you take no action to export correctly from InDesign and display the document in Acrobat using pdfGoHTML, this is what it may look like:

pdfGoHTML-Ansicht mit falscher Struktur

There are several serious deficiencies here in terms of accessibility:

  • Tags are not assigned correctly 
  • Semantic structure is missing (no structural difference between headings and body text)
  • InDesign’s list function has not been used
  • Alternative text for the image is missing

If you work with accessible documents and wonder what you need to pay attention to, I recommend the book “Barrierefreie PDF-Dokumente erstellen” from author Klaas Posselt and Dirk Frölich. It teaches all the necessary technical and legal requirements for creating accessible documents with Adobe InDesign. As of writing, the book is only available in German.

If you have taken all precautions to output a PDF with correct tags, pdfGoHTML will show you the following:

Korrekte Tag-Struktur

You can see the striking difference in the document structure, even though both documents are visually identical. pdfGoHTML immediately shows you the structural deficiencies in a clear way. This allows you to quickly track down these shortcomings.

Post image: Miguel Á. Padriñán (

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