How to add subtitles to a video automatically, for free
Three ways to subtitle a video without paying —inside the app, on your computer or with an SRT file—, when each one makes sense and how to review an automatic transcript in five minutes instead of an hour.
The first time you subtitle a video by hand you discover something uncomfortable: one minute of video is around a hundred and fifty rounds of pause, play, type, rewind. Half an hour for a one-minute video.
The good news is you no longer have to do that part by hand. Automatic transcription now gets almost everything right, and the real work comes down to reviewing. What you do have to decide is how you want the subtitles, because that determines which tool to use.
First: burned in or a separate file?
There are two kinds, and they don't do the same job:
| Burned in (part of the picture) | Separate file (SRT or VTT) | |
|---|---|---|
| What they are | Text that's part of the video, like a caption graphic | A separate text file with timings |
| Can be switched off | No | Yes, the viewer decides |
| Where they're used | Reels, TikTok, Shorts, Stories, LinkedIn | YouTube, Vimeo, websites, corporate video |
| Can be translated later | Not without re-exporting | Yes, by swapping the file |
| Design | You choose font, size and position | The player decides |
The rule of thumb: for social media, burned in, because many people watch with the sound off and won't switch anything on. For YouTube or your website, a file, because it can be translated, switched off and read by search engines.
If you need both, as often happens, make the file first: an SRT can be burned in later, but burned-in subtitles can't be turned back into a file.
Route 1: inside the app
The fastest option if the video is only going to one network:
- Instagram: in Reels and Stories, the captions sticker transcribes the voice and puts it on screen. You can change the style and fix words by tapping the text.
- TikTok: while editing, the captions option generates the text automatically and lets you review it before posting.
- YouTube: it generates automatic subtitles for most videos. In YouTube Studio, under subtitles, you can review them, correct them and publish them as the official track.
The downside is that the result stays in that app. If the same video goes to three places, you subtitle it three times.
Route 2: on your computer, with automatic transcription
If the video goes to several places, or it's long, it pays to do it once on your computer:
- Transcribe the audio. In the Polimake desktop app transcription runs with Whisper on your own machine: free, with no minute limit and without uploading the video anywhere. The text comes out with its timestamps. On Windows 11 you also have Clipchamp, which includes automatic subtitles in its free version.
- Review (below, how to do it quickly).
- Export: burned into the video for social media, or the timed text to upload to YouTube.
We cover it in more detail in free transcription on your computer with Whisper, including what computer you need.
Route 3: writing or fixing the SRT by hand
An SRT file is plain text you can open in Notepad. Each subtitle has three lines: a number, the in and out time, and the text.
1
00:00:01,200 --> 00:00:03,800
We only make this rice on Sundays.
2
00:00:04,000 --> 00:00:06,500
And it almost always sells out before two.
It's worth being able to read one even if you use an automatic tool, because fixing a typo in the SRT is faster than re-exporting anything. Note the comma before the milliseconds: with a full stop, many players ignore it.
How to review in five minutes, not an hour
Automatic transcription always fails in the same places. Check only those:
- Proper and brand names. "Polimake" may come out as "poly make"; your client's name, worse. Find and replace in one go.
- Numbers. "Fifteen" or "15", "2,000" or "two thousand": pick one rule and apply it everywhere.
- Words from another language. Borrowed terms sometimes get spelled in creative ways.
- Line breaks. About forty characters per line and two lines at most. If a sentence doesn't fit, split it where a speaker would pause, not in the middle of a name.
And one last pass on your phone, with the video at real size: it's the only way to see whether the subtitles cover a face or sit under the app's buttons. Video sizes for social media explains which areas the interface covers.
Why it's worth it
Subtitles aren't only for people who are hard of hearing, though that would be reason enough. They're for people watching on the train, at the office or with a sleeping baby. The reasons, at more length, are in why subtitle a video.
Frequently asked questions
How do you add automatic subtitles to a video for free?
With the network's own automatic transcription (Instagram, TikTok or YouTube) if the video is going to one place, or with a desktop program that transcribes the audio, such as the Polimake desktop app or Clipchamp on Windows, if it's going to several. Either way, review the text before publishing.
What's the difference between burned-in subtitles and an SRT file?
Burned-in subtitles are part of the picture and can't be switched off; they're what's used on social media. An SRT file is separate timed text that the player shows over the video; it can be switched on, off and translated, and it's the norm on YouTube and websites.
How many characters should each subtitle line have?
As a guide, about forty characters per line and a maximum of two lines on screen, with each subtitle visible for at least a second. If a sentence is longer, split it at a natural pause in speech.
Is automatic transcription reliable?
On clean audio it gets the vast majority of words right, but it fails predictably on proper names, brands, numbers and foreign terms. That's why you should always check those points and do a final pass watching the video with the subtitles on.
Can you upload subtitles to YouTube from a file?
Yes. In YouTube Studio, in the video's subtitles section, you can upload a timed SRT or VTT file, or paste the text without timings and let YouTube sync it automatically.