Subtitles on Facebook may fail to show up in your video for several reasons; One is that the Always Show Captions is turned Off in your Facebook account, the other is that the subtitles you uploaded are not compatible.
Format of subtitles on Facebook
Starting with the last problem, subtitles on Facebook must be in SRT format. I discovered this after uploading a WEBVTT version of my subtitles. The video editor of Facebook gave an error and advised me to change the name of the subtitle file as well. For English, it should use this naming convention: subtitlename.en_US.srt
First, I tried to simply change the name of the file without converting the WEBVTT file to SRT. The video editor accepted my lazy trick and let me upload the subtitle file, but it didn’t show up.
Converting a lengthy subtitle file is no fun, so I looked for an online converter and found one that did the conversion perfectly: https://subtitletools.com/ It works quite quickly as well. If you want to know more about creating subtitles, have a look at How to create captions/subtitles for video and audio in WebVTT, SRT, DFXP format
OK, so I uploaded the converted file, which was now a perfect SRT file and uploaded that. When finished, I tested the video. Still no subtitles. What was wrong now? After searching the help section, I found the reason: Always Show Captions was turned Off . Apparently that is the standard setting. To change that, you have to go to Timeline Settings:
Then, you get the following settings panel:
Select Videos at the bottom left (1) and there you see the Always Show Captions option (2). Just set it to On if it is turned off. Now the subtitles show up automatically when you view your video, or any video that has captions or subtitles.
What about subtitles for visitors?
Indeed, how do you know that your visitors have this option turned on?
The answer is, you don’t. And you don’t know whether they have muted videos or not. Fact is, a lot of people mute videos on Facebook automatically. So, if you want to make sure that subtitles are shown, you might want to integrate them directly into your video. Keep in mind that this only works if you know upfront that your target audience understands the language of the subtitles.
You can post the video on your own website (if you have one) and just link to the page via Facebook. Advantage is that you control control the video player’s behavior (see also How to embed a HTML5 video on your site).
Downside is that many Facebook users prefer viewing a video embedded on Facebook itself rather than clicking on an external link.
If you have the time, you could both; embed the video in Facebook and show the URL to a better or longer version of the video on your website.