altcheck: draft alt text and contrast fixes with a local open vision model

Description and use

altcheck is a CLI tool that drafts alt text for images and suggests contrast fixes, enabling freelancers to quickly audit and improve client web pages.

Problem

Freelance web developers need a quick way to identify missing or generic alt text and color‑contrast failures on client pages.

Outcome

altcheck quickly drafts alt text for missing or generic images and suggests contrast‑fix CSS, producing a reviewable report in about 20 s per image on a 2‑core CPU.

Workflow

• 1. Run altcheck <URL> from the command line.
• 2. Playwright loads the page and axe‑core checks the color‑contrast rule.
• 3. For each image, SmolVLM‑500M‑Instruct drafts a short alt sentence and flags decorative images.
• 4. The tool outputs a report.html with drafted alt text and CSS suggestions.
• 5. The developer reviews the drafts and updates the site accordingly.

Evidence

altcheck is a small command-line tool for freelance web developers. Give it one URL and it writes a local report.html.

Source

Images with a missing, filename-style or generic alt get a drafted alt text. Text that fails the color-contrast check gets a suggested color and a copy-paste CSS fix.

Source

On a 2-core CPU with about 2 GB of RAM, float32 ran out of memory, so it uses bfloat16 there and takes about 20 seconds per image.

Source

A freelancer or small agency fixing client pages. Running it over a page and fixing the obvious gaps takes minutes, so it could be sold as a quick accessibility tidy-up pass.

Source