| name | webrtc-spec |
| description | Search and fetch WebRTC specs from W3C and IETF: W3C WebRTC 1.0 (RTCPeerConnection, RTCRtpSender/Receiver/Transceiver, RTCDataChannel, RTCDtlsTransport, RTCIceTransport, RTCSctpTransport, RTCStatsReport), WebRTC-Extensions (simulcast, encoded transforms), WebRTC Stats, Media Capture and Streams (getUserMedia), Screen Capture, WebCodecs, WebTransport. IETF RFCs: 8825 (overview), 8826/8827/8828 (security), 8829+9429 (JSEP), 8831/8832 (data channels), 8834 (RTP in WebRTC), 8835 (transports), 8836 (congestion), 8837 (DSCP), 8866 (SDP, obsoletes 4566), 8445 (ICE), 8489 (STUN), 8656 (TURN), 5764 (DTLS-SRTP), 3711 (SRTP), 3550 (RTP), 6184 (H.264), 7798 (HEVC), 7741 (VP8), 7587 (Opus), 9725 (WHIP), draft-ietf-wish-whep (WHEP). Use when the user asks to look up an SDP attribute, verify an ICE behavior, check an RFC number for WebRTC, or find the canonical spec for a WebRTC feature.
|
| argument-hint | [query] |
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:
| Question | Page |
|---|
"What's the signature of addTransceiver?" | w3c-webrtc |
"What does a=msid mean?" | rfc-8866 |
| "How does ICE gather candidates?" | rfc-8445 |
| "What's in JSEP?" | rfc-9429 (obsoletes 8829) |
| "How is DTLS-SRTP negotiated?" | rfc-5764 |
| "What's the WHIP protocol?" | rfc-9725 |
| "How does simulcast work in SDP?" | rfc-8853 |
"What's a rid?" | rfc-8851 |
| "getUserMedia constraints?" | w3c-mediacapture-streams |
| "Screen-capture permission model?" | w3c-screen-capture |
| "WebCodecs frame formats?" | w3c-webcodecs |
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.
