Reading order

Reading order sets the sequence in which assistive technologies present content (WCAG 2.1, Success Criterion 1.3.2).

What is reading order?

Reading order determines the sequence in which software passes the content of a document on to users. Sighted readers infer the sequence from the layout. Assistive technologies, by contrast, rely on the data the author has stored in the file.

WCAG 2.1 covers this in Success Criterion 1.3.2 Meaningful Sequence, conformance Level A: when the sequence in which content is presented affects its meaning, a correct reading sequence can be programmatically determined. Two terms from the WCAG 2.1 definitions carry the criterion:

• Correct reading sequence: any sequence where words and paragraphs are presented in an order that does not change the meaning of the content. More than one correct order can therefore exist.
• Programmatically determined: determined by software from author-supplied data in a way that different user agents, including assistive technologies, can extract and present to users in different modalities. As an example for non-markup formats, WCAG 2.1 names technology-specific data structures exposed via an accessibility API that is supported by commonly available assistive technology.

For a PDF, this means: where the sequence carries meaning, it must be determinable from data in the file, not only from the visual page. In practice, that data is provided by the structure of a tagged PDF. Where the sequence carries no meaning, the criterion does not apply.

Legal basis and references

For documents, EN 301 549 V3.2.1 sets out reading order in clause 10.1.3.2: where ICT is a non-web document, it shall satisfy WCAG 2.1 Success Criterion 1.3.2.

• Clause 10.0: clause 10 applies to documents that are not web pages, documents that are not embedded in web pages, and documents that are provided with web pages but are neither embedded nor rendered together with them, i.e. downloadable documents. Documents in web pages, or embedded documents rendered together with the web page, fall under clause 9, there 9.1.3.2.
• Annex C, C.10.1.3.2: the type of assessment is inspection. The test is passed if the document does not fail Success Criterion 1.3.2. It is not applicable if the document contains no content relevant to the criterion.
• Annex A: Table A.1 (row 88) assigns clause 10.1.3.2 to documents and forms downloadable from a web page, Table A.2 (row 45) to documents and forms in mobile applications. Once the standard is cited in the Official Journal of the EU under Directive (EU) 2016/2102, conformance with these clauses confers, within the limits of the scope of the standard, a presumption of conformity with the corresponding essential requirements of that Directive.

How the laws in Germany and Austria refer to harmonised standards is explained in the article PDF/UA, WCAG 2.1 and EN 301 549 for documents. The standard itself is covered in the glossary entry EN 301 549.

Practical example

Check the reading order of every document whose layout departs from plain running text. Typical cases:

• PDF: a two-column report must lead through the left column first, then the right, in its document structure. If the structure mixes both columns line by line, the meaning changes and Success Criterion 1.3.2 is failed.
• Word: freely positioned text boxes and images can sit outside the text flow. Check that margin notes and captions are presented where they belong in the content.
• PowerPoint: on slides with several objects, check that titles, text boxes and graphics follow one another sensibly in the stored object order.

Further test steps are in the checklist for accessible documents in Word and PowerPoint. If you prefer not to remediate reports, forms or presentations yourself, you can have your documents made accessible.

See also

• Tagged PDF (tag structure)
• WCAG 2.1 (Web Content Accessibility Guidelines)
• EN 301 549 (harmonised standard for ICT accessibility)
• PDF/UA (ISO 14289)