name	youtube-downloader
description	Fetch existing YouTube transcripts/subtitles or archive spoken video content as text, and download YouTube videos/audio or HLS streams (m3u8) with yt-dlp and ffmpeg. Use for transcript/subtitle retrieval, text-first video archiving, video/audio downloads, protected streams with authentication headers, and download failures including nsig, 403 or browser-cookie issues.

YouTube Downloader

Overview

Enable reliable video and audio downloads from YouTube and HLS streaming platforms (Mux, Vimeo, etc.) using yt-dlp and ffmpeg. This skill provides workflows for:

YouTube downloads at available quality, with optional PO token and authorized cookie recovery
HLS stream downloads with authentication headers
Handling protected content and troubleshooting common download failures

Goal Split: File vs. Text (Read First)

Before downloading anything, classify the request:

User wants the video/audio file itself (save it, edit it, watch offline) → continue with the download flow below, unchanged.
User wants the spoken content as text (transcript, subtitles, meeting notes, archive, "what was said") → follow references/text-first.md FIRST: existing archived transcripts → platform transcript APIs → yt-dlp subtitle-only → authorized audio track + ASR. Do not download the full video just to obtain text.

The text-first route never blocks a file request: when the user wants the file, download it with the unchanged flow below.

Non-Technical User Experience (Default)

Assume the user is non-technical. Do not ask them to run commands. Execute everything yourself and report progress in plain language. Avoid mentioning tooling unless the user asks.

Default flow:

Ask for the URL (if not provided).
Fetch video metadata (title/uploader/duration/thumbnail) and confirm it matches the user's intent.
- If yt-dlp is blocked by “confirm you’re not a bot”, fall back to YouTube oEmbed for title/uploader/thumbnail (duration may be unknown).
Offer simple choices (video vs. audio-only, quality, subtitles, save location).
Proceed with sensible defaults if the user does not specify:
- Video download at best quality
- MP4 merged output
- Single video only (no playlists)
Download and report the final file path, file size, and resolution (if video).

Offer choices in user-friendly terms:

“Download the video in best quality (default)”
“Download audio only (MP3)”
“Pick a quality: 1080p / 720p / 480p / 360p”
“Include subtitles (if available)”
“Save to the Downloads folder (default) or tell me another folder”

Always render the thumbnail when available:

If metadata includes a thumbnail URL, include it using Markdown image syntax: ![Thumbnail](URL).

Ask before doing extra work:

Confirm playlist downloads (can be large).
Confirm installing/upgrading dependencies if missing.
Ask before extracting browser cookies.
If using cookies, never mention cookie counts or raw cookie details in user-facing responses. Say “used your Chrome login session”.
Set up a PO Token helper only after an explicit token diagnostic or a user request, and within existing installation/service authorization. If that authorization is already present, execute the recovery and resume the download. Otherwise request only the missing permission. Do not install Docker as a fallback; use the authorized browser provider when appropriate.

Legal/Safety reminder (brief):

Proceed only if the user has the rights or permission to download the content.

Response template (use plain language, no commands):

![Thumbnail](THUMBNAIL_URL)

Title: …
Channel: …
Duration: …

I can help you:
1) Download the video (best quality, MP4)
2) Download audio only (MP3)
3) Pick a specific quality (1080p/720p/480p/360p)
4) Include subtitles (if available)

Where should I save it? (Default: Downloads folder)

If the user says “just download”:

Proceed with defaults and confirm when the download finishes.
- If blocked, classify the actual diagnostic using the SOP below and execute the applicable authorized recovery.

Reliable Download SOP (Internal)

Read the download SOP before retrying a failure. Start with the current yt-dlp default clients and the existing network configuration. Do not require a provider, switch to Android, or extract browser cookies merely to begin a download.

Agent Execution Checklist (Internal)

Run scripts/download_video.py URL --info for metadata. It never starts a provider; its oEmbed fallback supplies limited fields when extraction fails.
Render the thumbnail when available. Use the requested file/audio, quality, subtitles and save location; proceed with defaults when already specified or implied.
Run the ordinary download first. With an installed Node runtime, pass --js-runtimes node when yt-dlp needs it; runtime installation still follows dependency authorization.
On failure, read the actual error and -F output. An absent requested format, images-only output, 403 or low resolution alone does not establish a token problem.
If a failed request explicitly reports a missing/required PO Token, read provider setup. Within existing setup authorization, execute --auto-po-token and finish the original download; do not stop at giving the user a command. This option attempts the native route first, then permits a bounded provider retry and WPC recovery.
Request browser-cookie permission before supplying either cookie option. Preserve the authorized cookie session and a compatible client throughout retries.
For an isolated 403/fragment failure, the wrapper can retry a quality preset once with progressive formats. Verify the resulting resolution; the fallback may be lower quality. Custom formats and audio-only requests keep their explicit selection.
Verify the final file with ffprobe and report its path, size and actual resolution or audio properties. Provider health or a format listing alone is not a completed download.

When to Use This Skill

This skill should be invoked when users:

Request downloading YouTube videos or playlists
Want to extract audio from YouTube videos
Experience yt-dlp download failures or limited format availability
Need help with format selection or quality options
Report only low-quality (360p) formats available
Ask about downloading YouTube content in specific quality (1080p, 4K, etc.)
Need to convert downloaded WebM videos to MP4 format for wider compatibility
Request downloading HLS streams (m3u8) from platforms like Mux, Vimeo, or other streaming services
Need to download protected streams that require authentication headers

Prerequisites

1. Verify yt-dlp Installation (Run this yourself)

which yt-dlp
yt-dlp --version

If missing or a current extraction diagnostic requires an update, obtain any missing install/upgrade authorization, then use the existing installation owner:

brew upgrade yt-dlp  # macOS
# or
pip install --upgrade yt-dlp  # Cross-platform

Check the current EJS setup guide for the JavaScript runtime and challenge-solver requirements of the installed distribution. An installed Node binary may need explicit --js-runtimes node; do not treat an EJS/nsig failure as a PO Token failure.

2. Check Current Quality Access (Run this yourself)

Before downloading, check available formats:

yt-dlp -F "https://youtu.be/VIDEO_ID"

Compare the listed media streams with the requested quality. If only a low-resolution format appears, inspect extraction/runtime warnings and the source availability before choosing recovery.

High-Quality Download Workflow

Step 1: Try the Native Client Selection

Keep player_client unset unless there is a specific diagnostic or explicit request. The official extractor guide describes yt-dlp's default attempt with clients that do not require tokens. Available formats depend on the video, account, client, network and current YouTube enforcement.

Step 2: Download and Escalate Only When Needed

# Download best quality up to 1080p
scripts/download_video.py "VIDEO_URL" --quality 1080p

# Download best available quality
scripts/download_video.py "VIDEO_URL"

# After an explicit token requirement, with setup already authorized
scripts/download_video.py "VIDEO_URL" --auto-po-token

For installation and provider-specific recovery, load PO Token setup. Do not infer a provider requirement from resolution alone.

Step 3: Verify Download Quality

# Check video resolution
ffprobe -v error -select_streams v:0 -show_entries stream=width,height,codec_name -of default=noprint_wrappers=1 video.mp4

Expected output for 1080p:

codec_name=vp9
width=1920
height=1080

Authorized Browser Cookies Method

Use cookies when the content requires the authorized account or a bot check persists, after cookie permission is granted. Cookies authenticate a session; they do not replace a missing PO Token:

# Firefox
yt-dlp --cookies-from-browser firefox -f "bestvideo[height<=1080]+bestaudio/best" "VIDEO_URL"

# Chrome
yt-dlp --cookies-from-browser chrome -f "bestvideo[height<=1080]+bestaudio/best" "VIDEO_URL"

Benefits: Access to age-restricted and members-only content. Requirements:

Must be logged into YouTube in the specified browser.
Browser and yt-dlp must use the same IP/proxy.
Preserve yt-dlp's default cookie-compatible clients; use web_safari only as a targeted retry. Do not combine account cookies with Android/iOS clients that do not support them.

Common Tasks

Audio-Only Download (Run this yourself)

Extract audio as MP3:

yt-dlp -x --audio-format mp3 "VIDEO_URL"

Custom Output Directory (Run this yourself)

yt-dlp -P ~/Downloads/YouTube "VIDEO_URL"

Download with Subtitles (Run this yourself)

yt-dlp --write-subs --sub-lang en "VIDEO_URL"

Playlist Download (Run this yourself)

yt-dlp -f "bestvideo[height<=1080]+bestaudio/best" "PLAYLIST_URL"

Convert WebM to MP4 (Run this yourself)

YouTube high-quality downloads often use WebM format (VP9 codec). Convert to MP4 for wider compatibility:

# Check if ffmpeg is installed
which ffmpeg || brew install ffmpeg  # macOS

# Convert WebM to MP4 with good quality settings
ffmpeg -i "video.webm" -c:v libx264 -preset medium -crf 23 -c:a aac -b:a 128k "video.mp4"

Parameters explained:

-c:v libx264: Use H.264 video codec (widely compatible)
-preset medium: Balance between encoding speed and file size
-crf 23: Constant Rate Factor for quality (18-28 range, lower = better quality)
-c:a aac: Use AAC audio codec
-b:a 128k: Audio bitrate 128 kbps

Tip: Conversion maintains 1080p resolution and provides ~6x encoding speed on modern hardware.

Troubleshooting Quick Reference

Missing Quality / Only Images / Requested Format Not Available

Inspect -F, the selected format expression, current yt-dlp/EJS/runtime warnings and source availability. These messages have multiple causes. Enter provider setup only when a failed extraction or media request also names a missing/required PO Token. Do not install a provider because a requested height or format ID is absent.

Sign in to Confirm You’re Not a Bot

Check that the intended proxy/network is in use. If the challenge persists and cookies are needed, obtain cookie authorization, retain that session, and retry. Stop with the exact authorization gap if it is unavailable; do not silently read browser cookies.

nsig / JavaScript Challenge Failure

Check the installed yt-dlp version and the EJS runtime and solver instructions. Repair the diagnosed prerequisite within authorization. Android or AndroidVR can be selected explicitly for a bounded diagnostic, but neither is the default recovery or a guaranteed solution.

403 / SSL EOF / Fragment Errors

Distinguish a media 403 from TLS, timeout, proxy and provider-health errors. A generic 403 does not prove a Token requirement. Check the network path first for SSL/timeout failures; retry only after a relevant change. The wrapper's single progressive retry applies to 403/fragment failures with quality presets, and may reduce quality.

Slow Downloads or Network Errors

For users in China or behind restrictive proxies:

Downloads may be slow due to network conditions
Allow sufficient time for completion
yt-dlp automatically retries on transient failures

PO Token Warning (Harmless)

WARNING: android client https formats require a GVS PO Token

Action: A successful, verified download needs no repair for an unused-client warning. On failure, read the full diagnostic and actual formats before choosing a token branch.

Bundled Script Reference

scripts/download_video.py

Use this wrapper for native-client downloads and bounded diagnostic recovery. It does not install/start providers or read cookies by default. Execute it yourself and report the verified file.

Basic usage:

scripts/download_video.py "VIDEO_URL"

Arguments:

url - YouTube video URL (required)
-o, --output-dir - Output directory
--output-template - Output filename template (yt-dlp syntax)
-f, --format - Format specification
-q, --quality - Quality preset (best, 1080p, 720p, 480p, 360p, worst). Default: best (skipped for --audio-only)
-a, --audio-only - Extract audio as MP3
--subtitles - Download subtitles if available
--sub-lang - Subtitle languages (comma-separated, default: en)
--cookies-from-browser - Load cookies from a browser (e.g., chrome, firefox)
--cookies-file - Load cookies from a cookies.txt file
--player-client - Use a specific YouTube player client (e.g., web_safari)
--auto-po-token - Authorize provider setup after a failed explicit missing/required-token diagnostic; try native clients first, then Docker bgutil or browser WPC
--no-auto-po-token - Disable provider setup (default); does not disable already-installed yt-dlp plugins
--proxy - Proxy URL for yt-dlp and the PO Token provider (e.g., http://127.0.0.1:1082)
--wpc-browser-path - Browser executable path for WPC provider
-F, --list-formats - List available formats
--merge-format - Merge output container (e.g., mp4, mkv). Default: mp4
--playlist - Allow playlist downloads (default: single video only)
--info - Print title/uploader/duration/thumbnail and exit
--no-android-client - Retained compatibility option; the wrapper already leaves native client selection unchanged
--js-runtimes - Pass an installed runtime to yt-dlp, e.g. node or node:/path/to/node

Quality Expectations

Do not promise a resolution based on a provider/client/cookie combination. Request the desired quality, inspect available formats, and verify the actual downloaded file. A successful high-resolution download without new provider setup proves only that input and environment; installed plugins or configuration may still contribute. A provider cannot create a resolution absent from the source.

HLS Stream Downloads (m3u8)

For streaming platforms like Mux, Vimeo, and other HLS-based services, use ffmpeg as the primary tool. These streams often require authentication headers that yt-dlp may not handle correctly.

Identifying HLS Streams

HLS streams use .m3u8 playlist files:

Master playlist: Lists multiple quality options
Rendition playlist: Contains actual video/audio segment URLs

Download Workflow

Step 1: Obtain the Stream URL

Get the m3u8 URL from the video source. For protected streams:

Open browser DevTools → Network tab
Play the video
Filter for "m3u8" to find the playlist URLs
Copy the rendition URL (usually contains quality info like "rendition.m3u8")

Step 2: Identify Required Headers

Many CDNs require authentication headers:

Referer: Origin website (e.g., https://maven.com/)
Origin: Same as Referer for CORS
User-Agent: Browser identification

Check the Network tab to see which headers the browser sends.

Step 3: Download with ffmpeg

Use ffmpeg with the -headers flag for protected streams:

ffmpeg -headers "Referer: https://example.com/" \
  -protocol_whitelist file,http,https,tcp,tls,crypto,httpproxy \
  -i "https://cdn.example.com/path/rendition.m3u8?params" \
  -c copy -bsf:a aac_adtstoasc \
  output.mp4

Key parameters:

-headers: Set HTTP headers (critical for authentication)
-protocol_whitelist: Enable required protocols for HLS
-c copy: Stream copy (no re-encoding, faster)
-bsf:a aac_adtstoasc: Fix AAC audio compatibility

Common header patterns:

# Single header
-headers "Referer: https://example.com/"

# Multiple headers
-headers "Referer: https://example.com/" \
-headers "User-Agent: Mozilla/5.0..."

# Alternative syntax
-headers $'Referer: https://example.com/\r\nUser-Agent: Mozilla/5.0...'

Handling Separate Audio/Video Streams

Some platforms (like Mux) deliver audio and video separately:

Download audio stream:

ffmpeg -headers "Referer: https://example.com/" \
  -protocol_whitelist file,http,https,tcp,tls,crypto,httpproxy \
  -i "https://cdn.example.com/audio/rendition.m3u8" \
  -c copy audio.m4a

Download video stream:

ffmpeg -headers "Referer: https://example.com/" \
  -protocol_whitelist file,http,https,tcp,tls,crypto,httpproxy \
  -i "https://cdn.example.com/video/rendition.m3u8" \
  -c copy video.mp4

Merge streams:

ffmpeg -i video.mp4 -i audio.m4a -c copy merged.mp4

Troubleshooting HLS Downloads

403 Forbidden Errors

Cause: Missing or incorrect authentication headers.

Solution:

Verify Referer header matches the video source website
Check if additional headers (Origin, User-Agent) are needed
Ensure the m3u8 URL includes all query parameters from browser

yt-dlp Stuck on Cookie Extraction

Symptom: Extracting cookies from chrome hangs indefinitely.

Solution: Use ffmpeg directly instead of yt-dlp for HLS streams.

Protocol Not Whitelisted

Error: Protocol 'https' not on whitelist 'file,crypto,data'

Solution: Add -protocol_whitelist file,http,https,tcp,tls,crypto,httpproxy

Empty Segments or No Streams

Cause: Expired signatures in the m3u8 URLs.