AI Alt Text for the Fediverse av Jon Henshaw

Make your Mastodon posts accessible to everyone.

AI Alt Text for the Fediverse adds a "Generate with Claude" button to the image-description (alt-text) field in the Mastodon web composer. Click it, and your image is described by Anthropic's Claude — using your own API key — producing a concise, screen-reader-friendly description that's filled in for you. Review and edit it, then post. Works on any Mastodon instance, including self-hosted ones.

Bring your own key — privacy first.
- You use your own Anthropic API key. There is no developer key in the add-on.
- It collects nothing and sends nothing to the developer — no analytics, no telemetry, no tracking.
- Your API key is stored only on your device and is never synced to the cloud.
- The only external service it contacts is Anthropic's API (api.anthropic.com), and only to describe an image or validate your key.

Accessibility best practices built in.
Claude is guided by established alt-text principles, aligned with W3C WAI image guidance. Descriptions are written for screen-reader and braille-display users — not for search engines. It classifies the image, front-loads the key information, transcribes any visible text verbatim, expands abbreviations, skips "image of…" lead-ins, and never invents details it can't see. You always review and edit before posting.

Cost transparency.
See a per-image cost estimate before you generate, and the exact cost afterward, with a running session total. Pricing is editable so you can keep it current with Anthropic's rates.

Choose your model.
Claude Haiku (default — fast and inexpensive) or Claude Sonnet (higher quality).

Requires an Anthropic API key from console.anthropic.com. Open source and MIT licensed.