How do I add subtitles to a video on my phone?
Videos you saved to your phone — downloads, recordings, clips from chats — almost never come with a subtitle track. On a computer you could install a browser extension, but mobile browsers do not support extensions. There is still a route that works: the local player, opened in your phone's browser.
Your phone videos have no subtitle track
Supported embedded text tracks can be translated directly; image subtitles need audio recognition. If no usable text track exists, choose audio recognition.
Why browser extensions do not work on mobile
The desktop extension is built for Chrome on a computer. Mobile browsers do not allow that kind of extension, which is why the phone route is different — it uses the local player instead of the extension.
The local-player route on mobile
- Open the WatchTranslate local player in your phone's browser.
- Sign in (signup includes free credits).
- Pick a video from your files or gallery.
- For audio recognition: Source language defaults to automatic detection; you can also set it manually. Choose the source and languages, then explicitly start translation. Choose the subtitle language and press play — subtitles are generated and shown as it runs.
Data and battery
Audio is read in about 30-second segments as the video plays, so you are not uploading the whole file. That keeps data use modest, though generating subtitles does require a network connection and uses more battery than plain playback.
What it does and doesn't do
- Local MP4/MKV files on phone or computer
- Works in mobile browsers (no app install)
- Failed runs do not consume credits
- Supported embedded text tracks can be translated directly; image subtitles need audio recognition.
- The browser extension cannot be installed on mobile
- No live streams
FAQ
Can I install the extension on my phone?
No — mobile browsers do not support the extension. On a phone, use the local player in your browser instead; it generates and translates subtitles the same way.
Is the video uploaded from my phone?
Not as a whole file. Audio is read in roughly 30-second chunks while you watch; the video stays on your device.
Will this drain my battery?
Generating subtitles uses more battery than plain playback because it streams short audio segments, but only while subtitles are being produced.
Does it cost anything?
Signup includes one-time free credits — roughly 20 minutes of video without subtitles. After that it is usage-based, at 1 credit per minute for generated subtitles.