WaxTap

WaxTap downloads and processes YouTube audio. It ships as a Go library and the waxtap CLI, both on the same processing core. Processing is opt-in: transcode, cut time ranges, drop SponsorBlock segments, measure or normalize loudness. A plain download keeps the selected source stream without re-encoding.

WaxTap targets public videos. Private, age-restricted, and login-gated videos are expected failures, not bypass targets. YouTube changes without notice; see MAINTENANCE.md when extraction breaks.

Highlights

• Pure-Go extraction via InnerTube and goja. No yt-dlp dependency.
• Token-free ANDROID_VR is the default. Full WEB audio is opt-in and needs an attested identity; forced iOS delivery is best-effort.
• One pure-Go pass can combine cuts, SponsorBlock removal, normalization, and transcoding, via the WaxFlow audio engine.
• Lossless output such as FLAC is still a re-encode of YouTube's lossy source. Only copy/remux avoids re-encoding.

The stable facade is the root waxtap package. YouTube code is isolated under youtube; audio processing lives in internal/media (a WaxFlow-backed engine) and internal/pipeline.

Requirements

• Go 1.26+

WaxTap is a single static binary with no external runtime dependency: all audio work (transcode, cut, normalize, probe) runs in-process via the pure-Go WaxFlow engine.

Install

go install github.com/colespringer/waxtap/v3/cmd/waxtap@latest   # CLI
go get github.com/colespringer/waxtap/v3                         # library

Release archives hold Linux, macOS, and Windows binaries for amd64 and arm64. Put waxtap on PATH and run waxtap --help. Unsigned macOS binaries may need xattr -d com.apple.quarantine /path/to/waxtap; Windows may prompt SmartScreen.

CLI

Media commands accept a YouTube URL or bare video or playlist ID. download also accepts a channel URL or bare UC ID, resolving to the channel's uploads feed. cut, transcode, and normalize also take local files. Every command has --help, and --json is a stable scriptable contract (schemaVersion 2).

waxtap info <video-url>                         # metadata and best audio
waxtap formats <video-url>                      # all audio formats
waxtap download <video-url> -o track            # keep source
waxtap download <video-url> --format flac -o track.flac
waxtap download <video-url> --sponsorblock --normalize --format mp3 -o track.mp3

waxtap transcode song.flac song.mp3
waxtap normalize song.wav --loudness-target -14 --format flac -o song.flac
waxtap normalize --album --format flac --dir ./normalized ./album/*.flac

waxtap download <playlist-url> -d ./music --download-archive archive.txt
waxtap download <channel-url> -d ./music        # channel uploads, newest first
waxtap download <channel-url> --list            # list entries, no download
waxtap doctor

info --show-url adds a signed, expiring stream URL and content length under resolved.*; treat that output as sensitive. info --full adds publish date and chapters via a token-free watch-page fetch.

transcode and normalize also take directories: -r recurses, --dir sets an output directory, and --force re-encodes files already in the target codec. Album normalization applies one gain to every track: --peak-mode cap leaves the true-peak limiter idle and reproduces the input's track-to-track spacing exactly on a lossless target, at the cost of landing short; the default limit reaches for the target and lets the per-track limiter compress that spacing. Loudness uses EBU R128 (integrated LUFS, true peak dBTP, range LU).

Notes

• --channels mono|stereo|surround|any picks a native layout, defaulting to stereo. It selects among a video's source streams, so it needs a URL input: on a local file or a directory it exits 2, unless --downmix is set too, where it names the fold target instead. (normalize --album and --measure-loudness reject it either way; neither writes a layout you chose.) --downmix allows surround-to-stereo/mono; it never upmixes, and on a file that already has the target layout it is a no-op that costs no re-encode. --itag names an exact encoding, so it overrides --channels; the run prints a note when the delivered layout is not the one asked for.
• --format names are case-insensitive and trimmed, and a few spellings are aliases: ogg for vorbis, m4a for aac, aif/aifc/afc for aiff, and remux for copy.
• --output-template takes {title}, {id}, {author}, {itag}, {ext}, and {index}. {index} numbers playlist items and expands empty for a single video, taking one adjacent -, _, or space with it: {index}-{title}.{ext} gives Song.opus. It takes only one, so a placeholder padded on both sides ({index} - {title}.{ext}) leaves the other separator behind as - Song.opus.
• --no-fallback disables watch-page, WEB-context, and incomplete-download fallbacks. Results report the client that actually delivered.
• Normalization applies one scalar gain. --peak-mode cap (the default) caps it so the true peak stays under -1.0 dBTP: transparent, but a source already peaking at 0 dBTP takes at most -1.0 dB whatever the target, so the miss can be 10 LU or more (reported as the loudness-target-missed warning). --peak-mode limit applies the full gain and lets the true-peak limiter catch the overshoot, at the cost of transparency. The limiter gives back part of the gain it is handed, so limit measures its own output and corrects, re-encoding up to 4 times to land within 0.3 LU of the target, and reports loudness-target-missed when the limiter saturates before reaching it. Ordinary material costs one extra encode pass. --album applies one gain in a single pass and defaults to limit; correcting per track would undo the spacing album mode exists to keep. Its cap clamps the one gain by the album's least true-peak headroom rather than per track, so the loudest track sets the headroom for all of them and the miss can be large. Both modes report a miss over 1 LU.
• Decoding runs in float, so output depth follows the decoded stream: a lossy source gives 32-bit float WAV, 24-bit FLAC, and AIFF-C float rather than plain AIFF. That is lossless but larger, and some older DAWs and hardware players reject float WAV. --bit-depth 16|24 forces integer output for wav/aiff/flac/alac; narrowing is dithered (TPDF), not truncated. The lossy formats encode in float and ignore it.
• --embed-thumbnail writes the video's thumbnail as front cover art, and --embed-metadata writes title, artist, date, and chapters. Chapter marks follow any cut: shifted by the audio removed before them, dropped when their content was removed. Both flags are best-effort: a failure warns and still delivers valid audio. WebM cannot hold a picture, so a cover-art request remuxes Opus-in-WebM to Ogg-Opus (lossless) when the output extension allows it. The image comes from the largest rung YouTube lists, and WaxTap also probes the deterministic 1280x720 endpoints when that ladder falls short of them.
• --cover-art square crops the embedded picture to the release art. A music "Art Track" composites square cover art onto a 16:9 canvas and letterboxes that into a 4:3 variant, and both sets of bars are pixels rather than metadata, so every player that resizes without cropping ships them. square peels the uniform borders and center-crops what remains; it never scales, so the art keeps its proportions and an image already square within 1% is left untouched. The default, --cover-art frame, embeds the delivered bytes verbatim.
• Processing a local file (transcode, normalize, cut, --album included) carries the input's embedded metadata - tags, cover art, chapters, synced lyrics - onto the rewritten output. Anything the output format cannot hold is reported as the tag-carry-incomplete warning, never dropped silently. Chapter marks follow a cut the same way the embed flags do. Tags describing the source audio itself (ReplayGain, encoder stamps) carry only on a pure --format copy remux; a re-encode or cut invalidates them, so they are left off.
• SponsorBlock requests get a 10-second budget, so a 429 there fails fast and exits 5 (rate limited) rather than waiting out a Retry-After it cannot outlast. On a download, --sponsorblock-on-error decides whether that is fatal or delivers the audio uncut with a warning.
• Playlist downloads support --concurrency, pacing, attempt limits, collision policies, and yt-dlp-compatible --download-archive files.
• --collision fail (the default) and auto-number claim the output path with the publish itself, so two single-file runs writing the same path cannot both report success: the loser exits 2 with the existing-file message and the winner's file is intact. overwrite opts into last-writer-wins. skip leaves the existing file alone and exits 0. On a single-file transcode, normalize, or cut it reports {"skipped":"exists"} with the path under --json, and prints that path under --quiet as a write does; download emits the same document without a path, and a directory batch reports the skip as one of its NDJSON item records. Two exceptions: normalize --album writes its tracks with a replacing rename, and on a filesystem without hard links (FAT, exFAT, some network shares) the publish degrades to a check-then-rename that a concurrent writer can still beat.
• waxtap cache dir and waxtap cache clean manage the persistent player-JS cache; --no-cache disables it.

Exit codes

The CLI maps failures to stable exit codes. The same class appears in --json as error.code. Run waxtap exit-codes for the built-in table.

Code	Meaning
0	success
1	unclassified error
2	invalid request/config, including a playlist or channel URL passed to a video command, unsupported input, or unavailable requested format
3	unavailable/restricted video or playlist (private, age-restricted, members-only, geo-blocked, removed), login required, live or upcoming, or no audio
4	extraction, cipher, or playlist parsing failure; WaxTap may need an update
5	rate limited
6	retired (formerly ffmpeg/ffprobe not found)
7	incomplete stream or expired stream URL
8	PO token required, missing, rejected, or not minted
9	network failure, including a proxy that is unreachable or rejects CONNECT, an unreachable sidecar, or an upstream HTTP error response
10	local I/O failure
130	canceled with SIGINT

Malformed targets exit 2; a well-formed but nonexistent or private video can only be classified after a network request and exits 3.

Library

package main

import (
	"context"
	"log"

	"github.com/colespringer/waxtap/v3"
)

func main() {
	client, err := waxtap.New(waxtap.Options{})
	if err != nil {
		log.Fatal(err)
	}

	_, err = client.Download(context.Background(), waxtap.Request{
		URL: "https://youtu.be/VIDEO_ID_01",
		ProcessSpec: waxtap.ProcessSpec{
			Transcode: &waxtap.TranscodeSpec{Format: waxtap.FormatFLAC},
			Output:    waxtap.ToFile("track.flac"),
		},
	})
	if err != nil {
		log.Fatal(err)
	}
}

A default Download (nil ProcessSpec) delivers the source stream byte-for-byte: no processing, SourceBytes == OutputBytes, Transcoded false. Library selection starts from LayoutAny and can rank a surround track highest; pass WithChannels(LayoutStereo) to match the CLI. Client.Enumerate expands a playlist or channel URL with Skip/Stop predicates for an archive cursor, and WithFullMetadata() adds publish date and chapters.

Availability failures (ErrVideoUnavailable, ErrAgeRestricted, ErrMembersOnly, ErrGeoBlocked, ErrLiveContent, ErrLiveNotStarted, and siblings) are typed sentinels a feed consumer should skip rather than treat as fatal; see the package doc's skip-vs-fail taxonomy. For full WEB SABR audio, wire a sidecar through NewSidecarPOTokenProvider, NewSidecarPlayerContextProvider, or NewSidecarSessionProvider (see below). example_test.go covers streaming, local processing, playlists, SponsorBlock, album measurement, metadata, and WEB SABR.

Configuration

CLI precedence, highest to lowest: explicit flag, WAXTAP_* environment variable, JSON config file, built-in default. The default file is config.json under os.UserConfigDir()/waxtap; override with --config or WAXTAP_CONFIG. Unknown JSON keys and malformed environment values are errors.

--json, --quiet, and --verbose are global. Other flags appear only on the commands that use them. Timeout values are seconds; keys with no flag are config/environment only.

Config key	Environment variable	Flag
cacheDir	WAXTAP_CACHE_DIR	--cache-dir
noCache	WAXTAP_NO_CACHE	--no-cache
tempDir	WAXTAP_TEMP_DIR	--temp-dir
proxy	WAXTAP_PROXY	--proxy
insecure	WAXTAP_INSECURE	--insecure
perHostQPS	WAXTAP_QPS	--qps
cooldownSeconds	WAXTAP_COOLDOWN	--cooldown
hl	WAXTAP_HL	--hl
gl	WAXTAP_GL	--gl
sponsorBlockBaseURL	WAXTAP_SPONSORBLOCK_BASE_URL	--sponsorblock-url
profileOverridePath	WAXTAP_PROFILE_OVERRIDE	--profile-override
chromeMajor	WAXTAP_CHROME_MAJOR	--chrome-major
poTokenURL	WAXTAP_POTOKEN_URL	--potoken-url
playerContextURL	WAXTAP_PLAYER_CONTEXT_URL	--player-context-url
client	WAXTAP_CLIENT	--client
sessionURL	WAXTAP_SESSION_URL	--session-url
visitorData	WAXTAP_VISITOR_DATA	--visitor-data
cookies	WAXTAP_COOKIES	--cookies
apiKey	WAXTAP_API_KEY	--api-key
channels	WAXTAP_CHANNELS	--channels
downmix	WAXTAP_DOWNMIX	--downmix
downloadConcurrency	WAXTAP_DOWNLOAD_CONCURRENCY	--concurrency (download)
procs	WAXTAP_PROCS	-
chunkParallelism	WAXTAP_CHUNKS	-
extractionTimeoutSeconds	WAXTAP_EXTRACTION_TIMEOUT	-
resolveTimeoutSeconds	WAXTAP_RESOLVE_TIMEOUT	-
webContextTimeoutSeconds	WAXTAP_WEB_CONTEXT_TIMEOUT	-
sponsorBlockTimeoutSeconds	WAXTAP_SPONSORBLOCK_TIMEOUT	-
chunkTimeoutSeconds	WAXTAP_CHUNK_TIMEOUT	-

PO tokens and WEB

ANDROID_VR is token-free for public videos. WEB-family clients use URL-less SABR/UMP audio, and complete delivery needs three things together: a GVS-scope PO-token provider (Options.POTokenProvider or --potoken-url), an attested identity (a /player-context handoff or an adopted /session), and a shared egress IP for the attesting service and the download. A PO token alone does not lift the WEB preview cap.

# Attested player context, adopted WEB session as fallback
waxtap download <url> --client web \
  --player-context-url http://127.0.0.1:4416/player-context \
  --session-url http://127.0.0.1:4416/session \
  --potoken-url http://127.0.0.1:4416/get_pot

WaxTap tries the attested player context first; if it fails or caps, the WEB chain can use the adopted session. Static adoption is also available with --visitor-data and optional --cookies. Library callers get the same handoff via the NewSidecar* providers, each taking a base URL or full endpoint plus an optional WithSidecarAPIKey; ParseNetscapeCookies loads a static session from a browser cookies.txt. See MAINTENANCE.md for sidecar contracts and SABR diagnostics.

Maintenance

waxtap doctor runs a low-cost extraction, resolution, and byte-read health check; waxtap doctor --full verifies complete delivery. The maintenance runbook covers dumps, profile refreshes, cipher failures, SABR changes, fixtures, and releases.

Acknowledgements

WaxTap was influenced by kkdai/youtube and yt-dlp, but ships no code from either and does not invoke yt-dlp.

Disclaimer

WaxTap is for personal and otherwise authorized use. You are responsible for complying with YouTube's Terms of Service and applicable law.

License

MIT.