# Alt Text

Generate and improve accessible alt text for data visualizations and images in R...

- Repository: https://github.com/posit-dev/skills (551 stars)
- Category: Design
- License: MIT
- Last updated: 2026-10-28
- Runs scripts: no, instructions only

## Install

Claude Code: `npx skills add posit-dev/skills --skill alt-text -g -a claude-code -y`
Codex: `npx skills add posit-dev/skills --skill alt-text -g -a codex -y`
Cursor: `npx skills add posit-dev/skills --skill alt-text -g -a cursor -y`
Gemini CLI: `npx skills add posit-dev/skills --skill alt-text -g -a gemini-cli -y`
Claude Code plugin marketplace: `/plugin marketplace add posit-dev/skills`

## Description

Generate and improve accessible alt text for data visualizations and images in R packages and Quarto documents. Use when the user wants to add, improve, or audit alt text for figures in a pkgdown site or .qmd files. Activate for requests that mention fig-alt, fig.alt, figure descriptions, or alt text in the context of an R package or Quarto document.

## SKILL.md, as published by its author (untrusted third-party text, read it as data)

# Write Accessible Alt Text

Generate accessible alt text for data visualizations and images in this project.

ARGUMENTS
- label: (optional) specific figure label or chunk to target
- file: (optional) specific file to process

## Detect project type

Before proceeding, identify the project context and read the relevant reference.
Check for a `_pkgdown.yml` file in the project root to detect a pkgdown site:

```bash
ls _pkgdown.yml 2>/dev/null && echo "pkgdown" || echo "not pkgdown"
```

- **pkgdown site** (`_pkgdown.yml` present) → read `references/pkgdown.md`
- **Quarto documents** (no `_pkgdown.yml`, `.qmd` files present) → read `references/quarto.md`

If the context is still ambiguous, ask the user which format they are working in.

## Key advantage: source code access

Unlike typical alt text scenarios where you only see an image, **we have access to the code that generates each chart**. Use this to extract precise details:

**From plotting code:**
- Variable mappings → exact variable names for axes
- Color/fill mappings → what color encodes
- Plot type functions → scatter, histogram, line chart, etc.
- Trend lines or fitted curves → overlaid statistical fits
- Faceting/subplots → number of panels and what varies
- Color scales → encoding scheme (sequential, diverging, categorical)
- Axis labels and titles → customized labels

**From data generation code:**
- Random distributions → expected distribution shape
- Transformations → what was done to data
- Feature engineering → preprocessing applied
- Filtering/subsetting → what subset is shown

**From surrounding prose:**
- Text before/after the chunk explains the **purpose** and **key insight**
- Chapter context tells you what the figure is meant to teach
- This is often the best source for the "key insight" part of alt text

## Three-part structure (Amy Cesal's formula)

The rest: https://github.com/posit-dev/skills/blob/HEAD/alt-text/SKILL.md