Alternative Text (Alt Text) for your Figures

What Is Alt Text?

Alternative text (also called alt text) is short meaningful text describing the contextually relevant aspects/elements of an image/graphic. In short, this text represents the image itself. Alt text should be 2–3 meaningful sentences. On average, alt text should be ~125 characters, but no more than 250 characters.

Go to alt text examples

Why Is Alt Text Important?

Alt text is an important part of digital accessibility. It serves as the text equivalent of an image/graphic. Alt text helps individuals with a visual disability or impairment or processing disorder who use assistive technology to access data. Types of assistive technologies include: screen readers, Braille displays, and audio/text-to-speech technology. It is important that all users have an inclusive equivalent experience with digital content.

The GAAD Foundation states: 1 billion people worldwide have disabilities (https://accessibility.day/). This is a significant portion of the population.

There are laws, standards, and guidelines in place to aid those with disabilities.

  • Web Content Accessibility Guidelines (WCAG) standards ensure those who have disabilities and/or use assistive technology can use electronic materials and websites. WCAG success criterion 1.1 on non-text content compliance requires that all non-text content have a text alternative that serves the equivalent purpose of the image. Note: Alt text is a minimum accessibility requirement and you cannot reach any WCAG conformance level (A, AA, AAA) without it.
  • Alt text for your figures is necessary for European Accessibility Act and ADA Title II compliance.

Writing Alt Text

When writing alt text for your figures, consider (and keep in mind) the following:

  • Be concise. Assistive technology cannot pause alt text.
  • The reason you are providing the figure/image/graphic. What is its purpose and intent for the reader?
  • Consider word choice and use.
  • Consider your audience and the user experience. It is important not to simply repeat the caption. The reader will have access to the caption. Figure captions and alt text serve different purposes.
  • Eliminate redundancy. Repetition can be cumbersome for a reader using assistive technology.
  • Please do not state “image” or “photo” at the start of an alt text description, assistive technology will state this. However, if it is a map, chart, or graph, state this at the start so the audience can prepare for the description that follows.
  • AI (artificial intelligence) can be helpful to use as a starting point when learning to write alt text, but check that its description is accurate.
  • Read aloud your final alt text to imagine how a screen reader will sound to a reader when the alt text is read. Or better yet, try using an actual screen reader.
  • Alt text should be an integral part of your manuscript workflow and included early in the process with your final manuscript.

The alt text for all figures should be uploaded as a single, separate file to our online peer review system using the “Alt Text” file type. Begin the alt text for each figure with an indicator such as “[[Figure 1 alt text]]” so editors can easily identify it

Keep in Mind

Alt text will be read aloud by assistive technology to the user. The text needs to be written as it is spoken.

Alt text should be brief, meaningful, and contextually relevant–Consider the audience that needs it. Writing alt text will get easier with practice. Accept the challenge and give it a try for your figures. After all, you know your science best!

Note:

  • Spell out Greek symbols as opposed to using the unicode symbol. For example, if you have an epsilon symbol, the word "epsilon" should be written.
  • Subscript and superscript formatting is not retained in alt text.

    Examples using superscripts and subscripts:
    a2 + b2 = c2
    a squared plus b squared equals c squared
    a to the second power plus b to the second power equals c to the second power

    Depending on the alt text, H2O could be written as:
    H2O (plain text)
    water
    water molecule

 

Alt Text Examples

A: Color seismic reflection profile of line 691-12 showing stratified reflectors to 10 km depth. B: Interpreted color seismic reflection profile of line 691-12 showing thrust faults, décollement, and basement.

Alt text: A: Color seismic reflection profile of line 691-12 showing stratified reflectors to 10 km depth. B: Interpreted color seismic reflection profile of line 691-12 showing thrust faults, décollement, and basement.
Figure caption: Figure 5. Depth-converted seismic data from line 691-12 (A) without interpretations and (B) with interpretations. Abbreviations are defined in Figures 3 and 6. Vertical exaggeration (VE) = 1×.
Credit: From Robinson and Cato (2026; https://doi.org/10.1130/2025.1225(12)).

Rounded gastrolith from the Coon Creek Formation shown with specimen label card and photographic scale for size reference.

Alt text: Rounded gastrolith from the Coon Creek Formation shown with specimen label card and photographic scale for size reference.
Figure caption: Figure 3. Photograph of cobble from the Coon Creek Formation interpreted to be a possible plesiosaur gastrolith (scale in cm).
Credit: From Gibson et al. (2026; https://doi.org/10.1130/2026.0075(04)).

Resources

Americans with Disabilities Act (ADA)
World Wide Web Consortium (W3C)
Web Accessibility in Mind
European Accessibility Act