// Use webspec-index to query WHATWG, W3C, and TC39 web specifications from the command line
| name | webspec-index |
| description | Use webspec-index to query WHATWG, W3C, and TC39 web specifications from the command line |
Query WHATWG, W3C, and TC39 web specifications from the command line.
Use webspec-index whenever you need to understand what a web spec says — algorithm steps, section content, cross-references, or whether a spec anchor exists. Specs are fetched and cached locally on first use.
Assume that all specs from WHATWG, W3C and TC39 are indexed. If in doubt, run webspec-index specs to list all spec names and their base URLs.
If webspec-index is not already available in your environment, you can install it via cargo:
cargo binstall webspec-index
# or
cargo install webspec-index
Always put the section identifier in quotes to avoid shell interpretation of #.
webspec-index query 'HTML#navigate'
webspec-index query 'DOM#concept-tree'
webspec-index query 'CSS-GRID#grid-container'
webspec-index query 'https://html.spec.whatwg.org/#navigate'
Returns the section's title, type (heading/algorithm/definition), full content as markdown, navigation tree (parent/prev/next/children), and cross-references. This is the primary command — use it to read what a spec section says.
Use --format markdown for human-readable output, or default --format json for structured data.
webspec-index search "tree order"
webspec-index search "navigate" --spec HTML --limit 5
Full-text search with snippets. Use --spec to narrow to one spec.
webspec-index exists 'HTML#navigate'
Exit code 0 = found, 1 = not found. Use this to validate anchor names before referencing them.
webspec-index anchors "*-tree" --spec DOM
webspec-index anchors "concept-*" --spec HTML
webspec-index anchors "dom-*assign*"
Glob matching (* wildcard). Useful when you know part of an anchor name but not the exact id.
webspec-index list DOM
Returns all heading-level sections with their anchors, titles, types, and depths.
webspec-index refs 'HTML#navigate' --direction incoming
webspec-index refs 'HTML#navigate' --direction outgoing
webspec-index refs 'HTML#navigate'
Shows which sections reference this one (incoming), which sections this one references (outgoing), or both (default). Useful for understanding how a concept connects across specs.
webspec-index update
webspec-index update --spec HTML
webspec-index update --force
Fetches latest spec versions. Uses 24h cache unless --force is given. Specs are auto-fetched on first query, so you rarely need this.
When working on a bug that references a spec algorithm:
# Read the algorithm you need to implement
webspec-index query 'HTML#navigate' --format markdown
# Check what concepts it references
webspec-index refs 'HTML#navigate' --direction outgoing
# Look up a referenced concept you don't understand
webspec-index query 'INFRA#ordered-set'
When you see a spec URL in code comments (e.g., https://html.spec.whatwg.org/#navigate), or a step comment like // Step 3.2, query the section to understand the algorithm:
webspec-index query 'https://html.spec.whatwg.org/#navigate'
When you know a concept but not its exact anchor:
# Search by text
webspec-index search "tree order" --spec DOM
# Or find by anchor pattern
webspec-index anchors "*tree*order*" --spec DOM
Before adding a spec URL to a code comment, verify the anchor exists:
webspec-index exists 'HTML#navigate' && echo "valid"
To see what other specs depend on a concept you're changing:
webspec-index refs 'DOM#concept-tree' --direction incoming