firefox-main/.claude/skills/webspec-index/SKILL.md

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---
name: webspec-index
description: Use webspec-index to query WHATWG, W3C, and TC39 web specifications from the command line
---
# webspec-index
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.
## Available specs
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.
## Installation
If `webspec-index` is not already available in your environment, you can install it via cargo:
```bash
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
```bash
webspec-index query 'HTML#navigate'
webspec-index query 'DOM#concept-tree'
webspec-index query 'CSS-GRID#grid-container'
```
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
```bash
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
```bash
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
```bash
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
```bash
webspec-index list DOM
```
Returns all heading-level sections with their anchors, titles, types, and depths.
### Cross-references
```bash
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
```bash
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:
```bash
# 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:
```bash
```
When you know a concept but not its exact anchor:
```bash
# 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:
```bash
webspec-index exists 'HTML#navigate' && echo "valid"
```
### Understanding cross-spec dependencies
To see what other specs depend on a concept you're changing:
```bash
webspec-index refs 'DOM#concept-tree' --direction incoming
```