WebVTT subtitles not showing on desktop player (Win, Mac)

Plex Players Desktop Players
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1

Server Version#: 1.42.1.10060
Player Version#: 1.110.0.351

Hi,

I’ve a show using WebVTT subtitle, and while they shows on Android player, they don’t on Desktop player (either Win or Mac).

Can you look into this?

Best,

2

You’re having much better luck than I am. 99% of my content with WebVTT subtitles refuses to play altogether. The server doesn’t consider it valid. I’ve had to transcode the subtitles to use SSA instead to even get them to play..

Sep 17, 2025 19:58:23.666 [139984896121656] ERROR - [Req#5f98] Couldn’t check for the existence of file “testfile.mkv”: boost::filesystem::status: Permission denied [system:13]: “testfile.mkv”

(it’s clearly not perms, it’s a+r)

root@plex:/# ffprobe testfile.mkv
ffprobe version 4.4.2-0ubuntu0.22.04.1 Copyright (c) 2007-2021 the FFmpeg developersbuilt with gcc 11 (Ubuntu 11.2.0-19ubuntu1
[matroska,webm @ 0x55de1cac6a00] Unknown/unsupported AVCodecID S_TEXT/WEBVTT.
[matroska,webm @ 0x55de1cac6a00] Could not find codec parameters for stream 2 (Subtitle: none): unknown codec
Consider increasing the value for the ‘analyzeduration’ (0) and ‘probesize’ (5000000) options
Input #0, matroska,webm, from ‘testfile.mkv’:
Metadata:
encoder : libebml v1.4.2 + libmatroska v1.6.4
creation_time : 2025-04-17T19:05:35.000000Z
Duration: 01:28:51.55, start: 0.000000, bitrate: 5014 kb/s
Stream #0:0: Video: hevc (Main 10), yuv420p10le(tv), 1920x1080 [SAR 1:1 DAR 16:9], 25 fps, 25 tbr, 1k tbn, 25 tbc (default)
Metadata:
BPS : 4756607
DURATION : 01:28:51.440000000
NUMBER_OF_FRAMES: 133286
NUMBER_OF_BYTES : 3169946169
_STATISTICS_WRITING_APP: mkvmerge v68.0.0 (‘The Curtain’) 64-bit
_STATISTICS_WRITING_DATE_UTC: 2025-04-17 19:05:35
_STATISTICS_TAGS: BPS DURATION NUMBER_OF_FRAMES NUMBER_OF_BYTES
Stream #0:1(eng): Audio: eac3, 48000 Hz, 5.1(side), fltp, 256 kb/s (default)
Metadata:
title : English
BPS : 256000
DURATION : 01:28:51.552000000
NUMBER_OF_FRAMES: 166611
NUMBER_OF_BYTES : 170609664
_STATISTICS_WRITING_APP: mkvmerge v68.0.0 (‘The Curtain’) 64-bit
_STATISTICS_WRITING_DATE_UTC: 2025-04-17 19:05:35
_STATISTICS_TAGS: BPS DURATION NUMBER_OF_FRAMES NUMBER_OF_BYTES
Stream #0:2(eng): Subtitle: none
Metadata:
title : English
BPS : 63
DURATION : 01:28:08.720000000
NUMBER_OF_FRAMES: 1210
NUMBER_OF_BYTES : 41908
_STATISTICS_WRITING_APP: mkvmerge v68.0.0 (‘The Curtain’) 64-bit
_STATISTICS_WRITING_DATE_UTC: 2025-04-17 19:05:35
_STATISTICS_TAGS: BPS DURATION NUMBER_OF_FRAMES NUMBER_OF_BYTES
Stream #0:3: Video: png, rgb24(pc), 600x337 [SAR 4724:4724 DAR 600:337], 90k tbr, 90k tbn, 90k tbc (attached pic)
Metadata:
filename : cover.png
mimetype : image/png
Unsupported codec with id 0 for input stream 2

3

Same here. Embedded WebVTT subtitles would not work on Android (phone or Shield).

Couldn’t figure out why videos would not play, and then noticed new sub format. Guessed that might be it, extracted and converted to SRT, then remuxed and it works.