How does an automatic subtitle generator work?

Speech recognition listens to the audio, writes down the words and records when each one was said. The words are grouped into readable lines with start and end times, which is what a subtitle file is.

Each account has 10 minutes of transcription per calendar month at no cost and with no card. Beyond that, prepaid minute packs are valid for 12 months.

What file types can I upload?

Any common video or audio file: MP4, MOV, MKV, WebM, MP3, M4A, WAV and more, up to 2 GB.

Very good on clear speech, with a few corrections typically needed for names and acronyms. Noisy audio, music with vocals and several people talking at once reduce accuracy.

Do I have to pick the language?

No. The spoken language is detected automatically.

Free automatic subtitle generator for video and audio

An automatic subtitle generator turns the speech in a video or audio file into timed text, without anyone typing. ToneLark is one that stays simple on purpose: upload a file, get an email, download SRT and VTT subtitles or a captioned copy of the video. No settings, no editor to learn, and the first 10 minutes every month are free.

How it works

Upload a video or audio file, up to 2 GB. It goes straight to secure storage in the EU.
Transcribe. The language is detected automatically and the speech becomes text with precise timecodes, word by word.
Download. Get the subtitles as SRT or VTT, or ask for a new MP4 with the captions burned in and the spoken word highlighted.

A typical video is ready a few minutes after the upload finishes. You get an email either way, so there is no need to keep the tab open.

What you can make with it

Subtitle files for YouTube, Vimeo and course platforms. Upload the SRT or VTT as a caption track. See how to add an SRT to YouTube.
Captions for your own website. The VTT file plugs into an HTML5 <track> element. See WebVTT subtitles for HTML5 video.
Burned-in captions for social media. A ready-to-post MP4 for Reels, TikTok and Shorts. See burn subtitles into a video.
A transcript for show notes, blog posts or search. Strip the timecodes from the SRT.
A starting point for translation. Send the SRT to a translator; the timing is kept.

Why the output is a file, not a locked-in project

Many subtitle tools keep your captions inside their own editor and charge to export. ToneLark gives you standard files. SRT and VTT open in every video editor, media player and platform, so you can finish the job wherever you already work. If you are unsure which format you need, SRT vs VTT explains the difference in two minutes.

Accuracy, honestly

Automatic transcription is excellent on a clear voice and gets worse as the audio gets harder: background music with vocals, echoey rooms, several people speaking at once, strong accents in a mix of languages. Expect to read the subtitles through once and correct a few words, mostly names. The audio tips cut that work down for the next recording.

Pricing

10 free minutes of transcription every calendar month, reset on the 1st (UTC). No card.
Minute packs for anything beyond that, valid for 12 months and used only after the free minutes.
A file has to fit in the minutes you have left; nothing is transcribed halfway.
If processing fails on our side, the minutes are returned.
Burning captions into the video does not use minutes.

Privacy

Files are used only to produce your subtitles, stored in the EU, and deleted automatically after about a day. Keep your original. The subtitle files stay in your dashboard until you delete the video.