Alternative Text (ALT) for Figures and Images

ALT is an accessibility requirement in digital publishing: it supplies a text equivalent for non-text content so that readers using screen readers can access the same informational content conveyed visually.

ALT is not the figure caption. Captions provide context (what the figure is, why it matters, how to read it). ALT describes what the figure shows so the evidence available to a sighted reader is available in text form.

Core principles

1. Informational equivalence. The ALT should convey the key information a reader would extract from the visual in the context of the manuscript’s argument.
2. Accuracy and restraint. Describe only what is present in the figure; avoid speculation, evaluation, or claims not supported by the image itself.
3. Specificity. ALT should distinguish the figure from other figures.
4. Proportional detail. Use brief ALT for simple figures; for complex figures, use brief ALT plus an extended description in the text, caption, or appendix.

Writing guidelines

Length

• Typical: 10–100 words.
• Preferred for most figures: one to two sentences (often about 25–40 words).

Do

• Begin directly with the description (avoid “In this figure…”).
• State the figure type when helpful (e.g., “line chart”, “spectrogram”, “map”, “syntax tree”, “flowchart”).
• For quantitative graphics, name axes/variables and units, when visible.
• State the main visible pattern (trend, contrast, clustering, distribution) that supports the manuscript’s point.
• Use plain, neutral language and standard punctuation.
• Write ALT in the same language as the manuscript.

Avoid

• Do not duplicate the caption.
• Do not begin with “Image of…”, “Figure showing…”.
• Do not include interpretations not supported by the figure itself.
• Do not use bullet lists, equations, or complex formatting inside ALT.
• Do not reuse identical ALT across different figures.

Decorative images

If an image is purely decorative and conveys no information needed for the manuscript (which is rare in research articles), it should be identified as decorative so that assistive technologies can ignore it. Decorative images must not be used to convey substantive content.

Complex figures and extended descriptions

For dense figures (multi-panel layouts, maps with many points, detailed schematics, high-density plots), CadLin recommends a two-layer approach:

1. Short ALT stating what the figure is and the principal information it conveys.
2. An extended description in the main text, caption, or appendix, capturing details that a sighted reader would extract visually.

Information required to follow the manuscript’s argument should not be available only in the figure. The manuscript text should state the principal results supported by the visual.

Guidance by figure type

Charts (line, bar, scatter)

• Specify chart type.
• Name axes/variables and units.
• State the main pattern relevant to the claim.

ALT example

Spectrograms, waveforms, and acoustic traces

• Specify representation (spectrogram, waveform, formant tracks, intensity curve).
• Identify the target segment or interval if marked in the figure.
• Describe salient visual cues used in the manuscript, without exhaustive detail.

ALT example

Maps

• State geographic scope and extent.
• Describe symbols and encodings (points, regions, routes, gradients).
• For many locations, use short ALT and provide an extended description or table.

Trees, diagrams, and flowcharts

• Describe components and relations (hierarchy, dependency, arrows, grouping).
• Summarize step or panel structure when needed.

Photographs and screenshots

• Describe only what is required for the manuscript’s purpose.
• Avoid personal attributes (age, gender, race) unless analytically necessary and directly relevant.

How to provide ALT in the manuscript

To support editorial processing (PDF and web publication), authors must associate each ALT clearly with its corresponding figure.

Option A (recommended)

Add a line immediately after each caption beginning with ALT:

Figure 2. [Caption]
ALT: [Alternative text]

Option B

Add a section at the end of the manuscript titled Alternative text for figures, listing one entry per figure (Figure 1, Figure 2, etc.).

Use of AI tools

AI tools may assist in drafting ALT, but authors remain responsible for accuracy, scope, and alignment with the figure and the manuscript. Any use of AI should be reported according to the journal’s AI-use disclosure policy, when applicable.