How do I write alt text for a scientific figure?

Describe what the figure shows and its key takeaway in one or two clear sentences, as if explaining it to someone who can't see it. State the figure type, the variables, and the main trend or result; avoid 'image of' and don't just repeat the caption verbatim.

How do I make a figure colourblind-safe?

Use a colourblind-safe palette (such as Viridis or Okabe-Ito), avoid distinguishing items by red vs green alone, maintain strong contrast, and add a second cue like shape, pattern, or direct labels so colour is never the only signal.

How to Make Accessible Scientific Figures

Accessible figures aren't just the right thing to do — they reach more readers, satisfy growing publisher and funder requirements, and are usually clearer for everyone. This guide covers the practical steps: colourblind-safe design, contrast, not relying on colour alone, readable text, and writing genuinely useful alt text.

Design for colour vision deficiency

Around one in twelve men has some colour vision deficiency, most often red-green. Use a colourblind-safe palette (Viridis, Cividis, or the Okabe-Ito set), and never distinguish categories by red versus green alone. Test your figure with a colourblindness simulator and in greyscale — if it still reads, you're in good shape. See our colour palette guide for specifics.

Never rely on colour alone

This is the single most important rule. Add a second cue to every distinction: different line styles (solid, dashed), markers (circle, triangle), patterns, or direct labels on the elements. That way the figure works in greyscale, for colourblind readers, and even in a bad photocopy.

Contrast and legible text

Keep strong contrast between text/data and background, avoid light text on busy images, and use a clean sans-serif font at a size that stays readable at final print size. Good contrast and type help low-vision readers and everyone reading on a small screen.

Writing good alt text

Alt text lets screen-reader users access your figure, and many journals and preprint servers now request it. Describe what the figure shows and its main takeaway in one or two clear sentences, as if explaining it to someone who can't see it: name the figure type, the variables/axes, and the key trend or result. Skip "image of," don't simply duplicate the caption, and keep it concise. For a complex multi-panel figure, summarise the overall message and point to the full detail in the caption or a long description.

A quick accessibility checklist

Before you submit, confirm: the palette is colourblind-safe; no information depends on colour alone; contrast is strong; text is legible at final size; the figure survives a greyscale test; and you've written clear alt text. Two minutes of checking makes your work readable to a meaningfully larger audience.

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