Whether or not subtitles are automatically displayed when you play something from your Library is based on several factors.
Configure Language Settings
You’ll first need to properly configure your language options. Setting the Subtitle Mode controls whether subtitles are automatically displayed when watching a media item or not.
Related Page: Account Audio/Subtitle Language Settings
Related Page: Languages
Forced Subtitles
In some cases, you may have an embedded subtitle track that is specifically flagged as “Forced”. In such cases:
- If Shown with foreign audio is enabled, the “Forced” subtitle will be used even if there is an audio track present that matches your preferred audio language (this is the behavior that most people expect and desire)
- If Always enabled is selected, the “Forced” subtitle will be treated as normal
Audio and Subtitle Track Languages
In order for Plex to be able to intelligently choose an audio or subtitle track, it first has to know what language(s) the available audio and subtitle tracks are.
For tracks embedded within the file, the language needs to be set appropriately for the audio or subtitle track. If the language is not set, you can do so using various tools (e.g. mkvtoolnix for MKV files).
Tip!: If the language for a track is not set (i.e. it is detected as “unknown”), it will be treated as if it does not match your preferred language settings.
For external subtitle files, you’ll want to ensure that the filename correctly includes the language code.
Related Page: Adding Local Subtitles to Your Media
Related Page: Agents