3.9 KiB
yt-dlp YouTube JS Challenge Fix (Fedora)
Problem
When running yt-dlp on Fedora, downloads may fail with the following warnings and errors:
WARNING: [youtube] No supported JavaScript runtime could be found.
WARNING: [youtube] [jsc:deno] Challenge solver lib script version 0.3.2 is not supported (supported version: 0.4.0)
WARNING: [youtube] 0qhgPKRzlvs: n challenge solving failed: Some formats may be missing.
ERROR: Did not get any data blocks
ERROR: fragment 1 not found, unable to continue
This causes subtitle downloads (and sometimes video formats) to fail silently, with the MP4 completing but subtitles being skipped.
Root Causes
- No JavaScript runtime installed — yt-dlp requires Deno or Node.js to solve YouTube's JS challenges
- Outdated yt-dlp — the bundled challenge solver script is behind the required version
- Remote challenge solver not enabled — the updated solver script must be explicitly fetched
Fix
1. Install Deno
Deno is not in the Fedora repos. Install via the official installer:
curl -fsSL https://deno.land/install.sh | sh
sudo mv ~/.deno/bin/deno /usr/local/bin/deno
deno --version
Alternatively, Node.js works and is available via
sudo dnf install nodejs.
2. Update yt-dlp
sudo pip install -U yt-dlp --break-system-packages
If installed via standalone binary:
yt-dlp -U
3. Enable Remote Challenge Solver
Add --remote-components ejs:github to the yt-dlp command. This fetches the latest JS challenge solver from GitHub at runtime:
yt-dlp -f 'bestvideo[vcodec^=avc]+bestaudio[ext=m4a]/bestvideo+bestaudio' \
--merge-output-format mp4 \
-o "/plex/plex/%(title)s.%(ext)s" \
--write-auto-subs --embed-subs \
--remote-components ejs:github \
https://www.youtube.com/watch?v=VIDEO_ID
4. Persist the Config
Create a yt-dlp config file so --remote-components is applied automatically:
mkdir -p ~/.config/yt-dlp
echo '--remote-components ejs:github' > ~/.config/yt-dlp/config
Maintenance
YouTube pushes extractor changes frequently. Keep yt-dlp current:
sudo pip install -U yt-dlp --break-system-packages
Tags
#yt-dlp #fedora #youtube #plex #self-hosted
Known Limitations
n-Challenge Failure: "found 0 n function possibilities"
Even with Deno installed, the remote solver downloaded, and yt-dlp up to date, some YouTube player versions can still fail n-challenge solving:
WARNING: [youtube] [jsc] Error solving n challenge request using "deno" provider:
Error running deno process (returncode: 1): error: Uncaught (in promise)
"found 0 n function possibilities".
WARNING: [youtube] n challenge solving failed: Some formats may be missing.
ERROR: [youtube] Requested format is not available.
This is a known upstream issue tied to specific YouTube player builds (e.g. e42f4bf8). It is not fixable locally — it requires a yt-dlp patch when YouTube rotates the player.
Workaround: Use a permissive format fallback instead of forcing AVC:
yt-dlp -f 'bestvideo+bestaudio/best' \
--merge-output-format mp4 \
-o "/plex/plex/%(title)s.%(ext)s" \
--write-auto-subs --embed-subs \
--remote-components ejs:github \
https://www.youtube.com/watch?v=VIDEO_ID
This lets yt-dlp pick the best available format rather than failing on a missing AVC stream. To inspect what formats are actually available:
yt-dlp --list-formats --remote-components ejs:github \
https://www.youtube.com/watch?v=VIDEO_ID
SABR-Only Streaming Warning
Some videos may show:
WARNING: [youtube] Some android_vr client https formats have been skipped as they
are missing a URL. YouTube may have enabled the SABR-only streaming experiment.
This is a YouTube-side experiment. yt-dlp falls back to other clients automatically — no action needed.
pip Version Check
pip show does not accept --break-system-packages. Run separately:
yt-dlp --version
pip show yt-dlp