From Plex

General Subtitle Support

Plex supports rich integration of subtitles with your media, whether the subtitle stream/track is embedded within the file or is a separate, external subtitle file. For supported subtitle formats, they can even be transcoded into a video as it is sent out to a mobile or streaming device. The Plex Media Server even includes an OpenSubtitles.org metadata agent source that can automatically find and download subtitles for your content in some circumstances. Subtitles are not currently supported on Windows.

Fully Supported Formats

These formats are supported as either embedded tracks or external subtitle files. They are compatible with being transcoded into a stream to a mobile or streaming client.

SRT
SMI
SSA (or ASS)

Partially Supported Formats

Some other subtitle formats may work in some circumstances or with particular clients. For instance, the Plex desktop clients generally support a much larger variety of subtitle formats, but some may only work if the client and Plex Media Server are on the same machine.

VOBSUB
PGS
SUB/IDX

Subtitle Screencast

We also recommend taking a few minutes to watch the excellent Subtitles Screencast, created by Atrus.

Configuring Language Preferences

By configuring your language preferences appropriately, Plex will be able to intelligently choose whether to display a subtitle track or not as well as which subtitle track to display if multiple are available. The preferences allow you to choose your preferred audio and subtitle languages as well as when subtitles should be displayed.

Open the Plex Media Server Preferences. On a Mac, this can be done from the OS X menubar or your Plex Media Server's Dock icon. On other platforms or if you're using the web-based Media Manager, you may access it by clicking Preferences at the top right of the Media Manager window.
Select the Languages tab

Choose your preferred Audio language
Choose how you wish for subtitles to be shown with the Subtitle mode option:
- Manually selected: Plex will never show subtitles by default unless you manually enable them for a particular video
- Shown with foreign audio: If Plex doesn't find an audio track matching your preferred audio language, then Plex will try to display an appropriate subtitle track (see below)
- Always enabled: Plex will try its best to always display subtitles and will use the following heuristics
  - If a subtitle is found matching your requested language, it will be shown (even if the audio language matches)
  - If there is an external subtitle file (i.e. a subtitle file next to the video file) it will be shown even if the language doesn't match
  - If there is a single subtitle embedded in the file, it will be used even if the language doesn't match
Choose your preferred Subtitle language

Limitations on Automatic Selections

In order for Plex to intelligently choose which audio track to play as well as to choose when and how to display subtitles, Plex must also know the language of a particular external subtitle file (see the External Subtitle section) or embedded audio or subtitle track. For embedded audio or subtitle tracks, the language must be tagged within the file, which may not be true depending on how you acquire your files. Analysis apps such as MediaInfo can tell you whether the language is specified for a particular audio or subtitle track

Configure Metadata Sources

You'll need to configure your Metadata Agent Settings appropriately so that your subtitles can be found correctly.

Open the Media Manager
Open the Metadata Agent Settings window
- For the web-based Media Manager, open the Preferences window and select the Agents tab
- For the native Mac Media Manager, click the Gear icon at the top of the Media Manager window

Once the Metadata Agent Settings window is open, there are two main areas you may wish to set.

Enable Local Media Assets

The Local Media Assets source is what will pick up and handle external subtitle files (see later section for more information), among other things. To ensure that external subtitle files are enabled:

Check the "Local Media Assets" source in the right pane for the applicable Metadata Agent selected from the left pane

Most people will probably want to ensure that "Local Media Assets" is enabled for Freebase (the default movie agent) as well as TheTVDB (default television agent) at minimum.

Configure OpenSubtitles.org Metadata Source

The OpenSubtitles.org source can automatically download subtitles for content in particular situations. See later section for additional information. To enable the OpenSubtitles.org source:

Check the "OpenSubtitles.org" source in the right pane for the applicable Metadata Agent selected from the left pane
With the OpenSubtitles.org source highlighted on the right, click the Preferences button
- Choose a primary subtitle language to try to automatically download
- You may optionally also choose a second language to try and download

Note!: You must set the OpenSubtitle Language preference to control what Subtitle files are downloaded. Setting the preferred language in the Plex Media Server Language preference only affects which language is selected - not which ones are downloaded.

External Subtitle Files

Plex supports several formats for external subtitle files. You'll want to ensure that you've followed the previous information to set your language preferences as well as to enable the "Local Media Assets" metadata source.

Compatible Formats

The following formats are currently supported:

SRT
SMI
SSA (or ASS)

Naming the Subtitle File

In order to be correctly matched to the library item, external subtitle files need to be named correctly. A correctly-named file will also indicate the language of the subtitle. To name the file correctly:

Name it the same as the corresponding video file
Append the language code before the file extension
The external subtitle file should sit in the same folder as the corresponding video file
The language codes are defined by the ISO-639-1 (2-letter) or ISO-639-2/B (3-letter) standard

Examples:

/Movies
   Avatar (2009).mkv
   Avatar (2009).en.srt

or

/TV Shows
   /Absolutely Fabulous
      /Season 2
         Absolutely Fabulous - s02e03.avi
         Absolutely Fabulous - s02e03.eng.smi

Additional Reading: List of language codes

Scanning and Adding the Subtitles

So, once you've named your external subtitle file appropriately and placed it in the correct location, it should be detected the next time that Section is scanned. However, the subtitle isn't actually added during the scan. Instead, the subtitle will be automatically added in one of two circumstances:

The metadata for the library item is refreshed
The user attempts to play the library item in a client

As soon as the subtitle is added from doing one of the above, it will be available for selection in the client.

Obtaining Subtitle Files

There are a multitude of sources to obtain subtitle files online. SRT format is the most common available and works well with Plex. Plex does not officially endorse or recommend any subtitle source. For convenience, though, here are some of the many possible sources (in alphabetical order):

OpenSubtitles.org Automatic Downloading

With the built-in OpenSubtitles.org metadata source, it is possible to have subtitles automatically downloaded for your content in many circumstances.

Subtitle files on the website are created for specific video files. The OpenSubtitles.org agent tries to match your specific/exact video file with a subtitle designed for that file. As such, videos that are downloaded from a common source are much more likely to have matches found than a video that was personally encoded from a DVD, for instance. This is one of the biggest limitations to the agent and one of the main reasons that it might not automatically pick up subtitles for you.

Other limitations:

No Subtitle Available for the Selected Language

Currently, there is no indication within Plex about Subtitle activity from OpenSubtitles. For example, if there is no SRT available for your language, you will just notice no subtitle is available. This will be addressed in a later version but currently, you can see what's going on by consulting the OpenSubtitles log:

Navigate to PMS Plug-in Logs/com.plexapp.agents.opensubtitles.log (see info about PlexNine_PMS_TipsTricks#Plex_Log_Files log files
Open the log file (on a Mac, it should open in the Console app; for other platforms, you can open it in a normal text editor)
Look for the item you're having trouble with. An easy way to do this is to open the log file, then the Media Manager, right-click the show and choose Refresh Metadata. The last entry in the log will be OpenSubtitles activity for that show.

Note in the example below No subtitles available for language indicates no match was found on the OpenSubtitles site:

2011-03-23 11:49:57,622 (-4faed000) :  INFO (core) - Looking for match for GUID 8320d96a482b0bd2 and size 1451430201
2011-03-23 11:49:58,759 (-4faed000) :  INFO (core) - No subtitles available for language eng
2011-03-23 11:49:58,760 (-4faed000) :  INFO (core) - Looking for match for GUID 8320d96a482b0bd2 and size 1451430201
2011-03-23 11:49:59,893 (-4faed000) :  INFO (core) - No subtitles available for language fre

A Mistimed Subtitle File was Fetched

There are many versions of shows available like Extended Versions, Special Editions etc with additional or deleted scenes. A subtitle file intended for the original show will have different timing to the 'Director's Cut'. In this case, subtitles will be displayed at odd or incorrect positions in the show. To fix this, download a subtitle file that you know matches your show's version and then handle it as an external subtitle file (see other section).

Upgrading from Plex 0.9.13 or Earlier

If you're upgrading from a Plex Library created with Plex 0.9.13 or earlier, the Sections need to be refreshed to pick up existing subtitles as well as to fetch them from OpenSubtitles.org. OpenSubtitles allow a certain number of subtitle fetches per day per IP address. If you're upgrading a large library, you may run into this limit. Try again in 24 hours to fetch more subtitles. To update your Library:

Ensure you have configured the Metadata and PMS Language preferences as before
Open the Section to refresh
Perform a Force-refresh of the Section by Shift-Clicking the Refresh button at the bottom right of the Media Manager window.

Using Subtitles

Once subtitles have been scanned in and recognized by the Plex Media Server, they are available for selection and use from within a Plex client. Consult the Client documentation for details.

Unofficial Subtitle Resources

Oncleben's Guide for TV Show Subtitles

This trick uses TVShows2, Transmission, Plex and eventually Soleol. Set them up once as described and just wait episodes release in your couch ;-). Read 'how to' on this post: Get new TV shows episodes with subtitles in Plex automatically

Languages:

English

main

PlexNine PMS Subtitles