Accessible publishing
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3 Principles for producing accessible publications

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Accessible digital publications must be:

  • able to be perceived through at least one of the user’s senses;
  • operable by the user;
  • understandable, using consistent interfaces and simple language; and
  • robust – working across different devices, platforms, browsers and assistive technologies (W3C, 2023a).

Specific rules for the production of accessible publications are set out below. See also 2.1.6 Accessibility in “Graphic design guidelines” of Publishing at FAO.

3.1 Semantic structure and navigation

Clear semantic structure and navigation are the backbone of accessible publications, enabling users to understand where they are in a publication and how to move to another part of it. Structure and navigation help users understand the relationship between different content elements.

As outlined by the World Wide Web Consortium, good practice in accessible web navigation involves using hierarchical headings (<h1> through <h6>), landmarks (which programmatically identify sections of a page) and menus, as well as labelling interactive elements like links, buttons, forms and lists. Menus should be labelled as menu buttons and must be focusable (i.e. the user can move focus to it via any input device), functioning and key-operable (W3C, 2023d).

Similarly, to produce accessible PDFs, it is vital to create a hierarchy of logical structure elements like headings and subheadings, and to tag all elements of the publication correctly. The tags determine the reading order of the PDF and guide the user through the content, while ensuring that non-text elements like figures and images are not skipped over by a screen reader. The process requires either adding tags to a non-tagged PDF or preparing a tagged PDF from InDesign. When working in InDesign, paragraph styles need to be set and applied consistently. Each style’s export tagging must be set based on its role in the document, e.g. paragraph (<p>), heading (<h1> to <h6>), etc. Tags must be in the proper sequence to ensure a smooth reading order for screen readers and assistive technologies. The tab key is used to navigate from one element to the next, and the tab order should reflect the structure of the document. To check the reading order and the tab order, the document can be viewed in Reflow view (WIPO, 2023).

3.2 Alternative text

Alternative text (alt text) is a type of metadata that makes images accessible. It describes non-text elements so that screen readers and assistive technologies can convey the meaning of the image to users with visual impairments (as well as in cases where it may not be loading due to an unstable internet connection). Alt text also optimizes the search engine rating of a publication and thereby increases its visibility and discoverability. Alt text is concise and differs from captions, which usually provide more detailed information about the image.  

Alt text should be written for all non-text elements that convey meaning such as figures, maps, photographs and brand elements like logos. However, embellishments, visual styling, watermarks and functional graphic elements such as headers, footers and decorative images do not need alt text and should be marked as “artifacts” in PDFs (WIPO, 2023) or using an empty alt attribute in other formats, which instructs screen readers and assistive technologies to skip over them (W3C, 2023e).

Alt text should be clear, concise, informative and non-repetitive. It should sum up the key messages and purpose of the image in two to three sentences (IAMLADP, 2022). Longer descriptions and analyses of graphs should be in the body text of the publication. It is not necessary to state that an image is a “graphic” or to describe the format, as screen readers and assistive technologies can detect it. However, indicating specific types of figures is important, e.g. a bar chart or a plot diagram. Hyperlinks and notes should not be included in alt text as they obstruct readability and understanding (WID, 2024).

For complex images like graphs, charts, diagrams and maps, it can be beneficial to have both short and long alt text. The former identifies the image and indicates where the long description can be found, while the latter describes the key messages in more detail. It is not helpful to have long lists of data points or literal readouts of data. For complex images, it is beneficial to provide a contextual summary with key highlights (W3C, 2024). See also 3.4 Tables and spreadsheets.

3.3 Colour contrast

Colour contrast is particularly helpful for users with colour blindness or low vision as it facilitates readability. Contrast should increase as the font size decreases. The Web Content Accessibility Guidelines (WCAG) 2.2 recommend the following contrast ratio between font size and color:  

  • for large text (14pt bold or 18pt regular), a 3:1 contrast with the background; and
  • for small text, a 4.5:1 contrast with the background (W3C, 2023f).  

Together with the use of large text and alt text, high contrast is particularly important for the accessibility of figures.  

Colour should never be used as the sole means to communicate data as many users cannot distinguish specific colours. Reds and greens are particularly difficult to discern. Secondary markers, such as shapes or symbols, should be used in addition to colour. Avoid flashing or blinking content.

3.4 Tables and spreadsheets

Accessible tables require correct formatting (row and column headers) and structural markup that defines the relationship between headers and data cells. This is vital as screen readers read aloud every cell and reference the header cells to maintain context for the user (WID, 2024). Merged or split cells should be avoided. Tables should not be nested inside larger tables. Spreadsheet workbooks must have unique tab names and blank worksheets should be removed. In PDFs, rows or tables should ideally not be split by page breaks.

Static images of tables such as .jpg or .png should not be used as this obstructs readability (WID, 2024). Tables should always be native and labelled properly within the page. To learn more about best practices for accessible tables, see the W3C Tables Tutorial (W3C, 2023c).
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