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Open source · Quality & Testing

Accessibility Snapshot Diff

Compare accessibility snapshots for regressions in rendered routes.

v0.1.0 · Node.js 22+ · MIT

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accessibility-snapshot-diff compares two already-exported accessibility-tree snapshots. Stable opaque node IDs locate structural and accessible-name regressions without printing potentially private names. It does not launch a browser or inspect a live page. Node.js 22+; zero dependencies.

This walkthrough uses the tool's public README and checked-in example files. Run the command from a repository checkout with Node.js 22+.

Run the checked-in example

node bin/accessibility-snapshot-diff.mjs --root examples --input passing.json
node bin/accessibility-snapshot-diff.mjs --root examples --input failing.json
npm run check

Read the result

The passing example exits 0; the failing example exits 1 for a removed button name and changed heading level. Invalid CLI configuration exits 2 with empty stdout. Unreadable or unusable export evidence exits 2 with an incomplete JSON report. Stdout is otherwise exactly one JSON report. The real input path must remain inside the real --root.

Scope

Strict UTF-8; maximum 1,048,576 input bytes, 300 nodes per snapshot, 50 ignored IDs, JSON depth 4 (root is 0), 5,000 ms injected processing time. Exact N and N+1 boundary tests cover every bound. IDs and roles are 1–128 code units; names at most 512 code units. Duplicate JSON keys, including escaped spellings, and unknown fields are refused.