Webrtc Spec

webrtc-spec

Context: $ARGUMENTS

Search and fetch W3C + IETF WebRTC specifications. A companion to webrtc-pion, webrtc-mediasoup, webrtc-livekit — this skill is your source-of-truth for what the wire protocol and browser API actually require.

Quick start

• Find an SDP attribute / RFC number: → Step 2 (search --query <term>)
• Read a full section: → Step 3 (section --page <page> --id <anchor>)
• Dump a whole doc: → Step 4 (fetch --page <page>)
• Print the RFC table: → Step 5 (list-rfcs)
• Prime the cache offline: → Step 6 (index)

When to use

• Before telling the user what an SDP attribute means, verify it against RFC 8866 (NOT RFC 4566, which is obsoleted).
• Before mentioning a WebRTC JS API method, verify it against the current W3C WebRTC 1.0 (REC).
• Need to cite the canonical URL for an RFC / TR (https://datatracker.ietf.org/doc/html/rfcN or https://www.w3.org/TR/<name>/).
• Choosing between two RFCs (e.g. SDP: 4566 vs 8866 — 8866 wins; JSEP: 8829 vs 9429 — 9429 is the newest update).

Step 1 — Page catalog

uv run ${CLAUDE_SKILL_DIR}/scripts/webrtcdocs.py list-pages

Top picks:

Full catalog in references/rfc-index.md.

Step 2 — Search

uv run ${CLAUDE_SKILL_DIR}/scripts/webrtcdocs.py search --query "rtcp-fb" --limit 5
uv run ${CLAUDE_SKILL_DIR}/scripts/webrtcdocs.py search --query "a=candidate" --page rfc-8866

Hits print page:line — heading, the canonical URL, and ±3 lines of context. First run fetches + caches; subsequent runs are instant.

Step 3 — Read one section

uv run ${CLAUDE_SKILL_DIR}/scripts/webrtcdocs.py section --page rfc-8866 --id 5
uv run ${CLAUDE_SKILL_DIR}/scripts/webrtcdocs.py section --page w3c-webrtc --id dom-rtcpeerconnection

--id accepts either a heading keyword or a numeric section like 5.13.

Step 4 — Fetch a whole page

Rarely needed — search + section is usually enough. Use for offline copies:

uv run ${CLAUDE_SKILL_DIR}/scripts/webrtcdocs.py fetch --page rfc-9725 --format text

Step 5 — Print the RFC table

uv run ${CLAUDE_SKILL_DIR}/scripts/webrtcdocs.py list-rfcs

Prints each RFC in the catalog with its number, short title, and canonical URL. Same data also in references/rfc-index.md for inline reading.

Step 6 — Prime the cache

uv run ${CLAUDE_SKILL_DIR}/scripts/webrtcdocs.py index

Fetches every known page to ~/.cache/webrtc-spec/. Override with WEBRTC_DOCS_CACHE=/path env.

Gotchas

• SDP is RFC 8866, not RFC 4566. 8866 obsoletes 4566 (2020). If Claude has trained on older material, it will likely cite 4566 — don't.
• "RFC 8854" is NOT SDP. 8854 is "FEC Requirements for Real-Time Text". Easy confusion because of proximity to 8866. Always verify via list-rfcs.
• JSEP has two RFCs. The original 8829 + the update 9429. For new work prefer 9429. Old blog posts cite 8829.
• WHIP is RFC 9725. It is final, not a draft. WHEP is still draft-ietf-wish-whep-NN — use the Datatracker "latest draft" URL.
• Trickle ICE is RFC 8838, separate from the base ICE RFC 8445.
• BUNDLE = RFC 9143. Older blog posts reference draft-ietf-mmusic-sdp-bundle-negotiation — cite 9143 instead.
• ICE + DTLS carriage in SDP is RFC 8843. Separate from ICE itself (8445) and from DTLS-SRTP (5764).
• Simulcast = RFC 8853; rid = RFC 8851; mid is a core SDP attribute living in RFC 8843 / 5888 depending on context.
• H.264 RTP = RFC 6184, HEVC = RFC 7798, VP8 = RFC 7741, VP9 payload is still in IETF draft land. Opus = RFC 7587 (+ draft updates).
• W3C URLs vs IETF URLs. W3C TRs live at https://www.w3.org/TR/<name>/ (published) or <name>/drafts/. IETF RFCs live at https://datatracker.ietf.org/doc/html/rfcN. Don't mix them.
• mediacapture-streams is the getUserMedia spec. Not "WebRTC Media" — that's colloquial.

Examples

Example 1 — "What does a=setup mean?"

uv run ${CLAUDE_SKILL_DIR}/scripts/webrtcdocs.py search --query "a=setup" --page rfc-8843

Cite RFC 8843 §5 ("Role-less" ICE handling) — a=setup:actpass|active|passive|holdconn.

Example 2 — "Is trickle ICE standardized?"

uv run ${CLAUDE_SKILL_DIR}/scripts/webrtcdocs.py search --query "trickle" --limit 5

Points at RFC 8838.

Example 3 — "What are valid RTCP feedback types?"

uv run ${CLAUDE_SKILL_DIR}/scripts/webrtcdocs.py search --query "rtcp-fb" --limit 10

Scope to rfc-8866 (syntax) and rfc-5104 (AVPF — referenced but not in our catalog).

Example 4 — "What's WHIP's authentication model?"

uv run ${CLAUDE_SKILL_DIR}/scripts/webrtcdocs.py section --page rfc-9725 --id 4

Section 4 — Bearer tokens, one-time POST to ingestion URL, 201 + Location header.

Example 5 — "Where is createOffer defined?"

uv run ${CLAUDE_SKILL_DIR}/scripts/webrtcdocs.py search --query "createOffer" --page w3c-webrtc

Troubleshooting

unknown page: foo

Cause: typo'd name. Solution: list-pages to see valid names. Common mistake: sdp — use rfc-8866.

urlopen error [SSL: CERTIFICATE_VERIFY_FAILED]

Cause: out-of-date system CAs. Solution: install/update certifi or run the macOS Install Certificates.command. Don't disable SSL verification.

Search returns nothing

Cause: wrong page or term is in a sibling RFC not in our catalog. Solution: drop --page, try broader term, or check list-rfcs for adjacent RFCs.

Results look truncated

Cause: text extraction flattens complex IETF tables. Solution: open the canonical URL printed in the hit — that's the authoritative view.

Reference docs

• Read references/rfc-index.md when you need the full RFC table grouped by topic (ICE/STUN/TURN, media transport, SDP, DTLS/SRTP, codecs, signaling, WHIP/WHEP, data channels, congestion, security).
• Read references/sdp-grammar.md when debugging an SDP offer/answer — covers a=rtpmap, a=fmtp, a=rtcp-fb, a=extmap, a=msid, a=ssrc, a=ice-ufrag/ice-pwd, a=candidate, a=fingerprint, a=setup, a=mid, a=rid, a=simulcast, a=sctp-port.