webspec-index

Query WHATWG, W3C, IETF 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.

Available specs

Assume that all specs from WHATWG, W3C, IETF and TC39 are indexed. If in doubt, run webspec-index specs to list all spec names and their base URLs.

Installation

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

Commands

Always put the section identifier in quotes to avoid shell interpretation of #.

Look up a spec section

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'
webspec-index query 'DOM#concept-tree'
webspec-index query "RFC9000#section-22"
webspec-index query "draft-ietf-tsvwg-sctp-dtls-chunk#name-security-considerations"

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.

Search across specs

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.

Check if a section exists

webspec-index exists 'HTML#navigate'

Exit code 0 = found, 1 = not found. Use this to validate anchor names before referencing them.

Find anchors by pattern

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.

List all sections in a spec

webspec-index list DOM

Returns all heading-level sections with their anchors, titles, types, and depths.

Cross-references

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.

Update 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.

Usage patterns for Gecko development

Understanding what you're implementing

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'

Finding the right spec section

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

Verifying spec anchors

Before adding a spec URL to a code comment, verify the anchor exists:

webspec-index exists 'HTML#navigate' && echo "valid"

Understanding cross-spec dependencies

To see what other specs depend on a concept you're changing:

webspec-index refs 'DOM#concept-tree' --direction incoming