Add subtitles to a video, automatically
Upload your video: Whisper AI turns the speech into synced subtitles, which you edit and style before exporting an MP4 with burned-in captions, or an SRT or VTT file. Nothing is uploaded.
- Whisper AI
- TikTok / Shorts style
- Burned-in MP4, SRT, VTT
- Video stays on your device
100% private — Everything is processed directly in your browser: your files, voice, and image are never sent to Chatzam's servers.
How do you add subtitles to a video?
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Upload the video
Choose a video up to 10 minutes long (5 minutes recommended) and the spoken language, or automatic detection. You can also import an existing SRT file.
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Edit and style
Review each subtitle and adjust its text, start and end, then choose the size, color, outline or background box, position and all caps.
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Export
Download the MP4 video with burned-in subtitles, or just the SRT or VTT file.
Automatic subtitles, ready for every platform
AI transcription
Whisper recognizes speech right in your browser and splits the text into short subtitles, synced with the voice.
Every subtitle editable
Fix a word or a name, shift a subtitle's start or end. Already have an SRT file? Import it instead of transcribing.
“TikTok / Shorts” style
Size, color, outline or background box, position at the bottom, middle or top, all caps: the preview updates live on the video.
Burned in or as a file
The MP4 burns the subtitles into the picture, visible everywhere, even on Instagram and TikTok. The SRT or VTT file alone is for YouTube or a video editor.
Burned-in captions or an SRT file: which should you choose?
An SRT or VTT file contains only the text and timings, for example “00:00:01,000 --> 00:00:03,500” in SRT (VTT uses a period instead of the comma). It's added alongside the video: on YouTube, in the Subtitles tab of YouTube Studio, viewers can then turn the captions on or off, and you can fix them later. Burned-in subtitles, also called open captions, are part of the picture: you can't turn them off or edit them afterwards, but they show up everywhere, in your style. That's the way to go for Instagram, TikTok, WhatsApp or a video sent as a file, where you can't attach an SRT.
Automatic subtitles: how they work, and what to check
The first time you use it, the Whisper model (about 40 to 150 MB) is downloaded once, then transcription runs on your computer. Processing time depends on your computer's power and the video's length: that's why 5 minutes is recommended, and 10 minutes is the maximum. For a longer video, trim it first with “Cut / Trim Video”. Whisper is reliable with a clear voice, but always proofread: names, numbers, words that sound alike, and passages with music or several people talking at once are where the mistakes pile up. Automatic language detection relies on the start of the audio: if the video opens with music, choose the language yourself.
Readable captions on TikTok, Reels and Shorts
Lots of videos are watched with the sound off, on the bus or at the office: without captions, the message doesn't get through. For vertical videos, the “TikTok / Shorts” style works well: big text, in all caps, with a thick outline or a background box so it stays readable on any background. Go for the middle position: at the very bottom of the screen, the caption, account name and app buttons may cover the text. Keep subtitles short enough to read at a glance, and check in the preview that none disappears too quickly. To get just the text of a recording, use “Transcribe Audio to Text”; to shrink the final video, use “Compress Video”.
Frequently Asked Questions
How do I add automatic subtitles to a video?
Upload the video, choose the language and start the transcription: Whisper AI creates synced subtitles. Review them, pick a style, then export the MP4 with burned-in subtitles.
How do I burn subtitles into a video?
Export as MP4: the subtitles become part of the picture and show up on every player and social network. You can start from an automatic transcription or from an SRT file you already have.
How do I add an SRT file to a video?
Upload the video, then import the SRT file instead of transcribing: the subtitles appear on the preview, editable, and you can burn them into an MP4. For YouTube, you can also upload the SRT on its own in YouTube Studio.
How long can the video be?
10 minutes max, 5 minutes recommended, since all the work happens on your computer. For a longer video, split it into several parts with “Cut / Trim Video”.
Is my video uploaded to a server?
No. Only the AI model is downloaded, once; transcription and burning in happen in your browser, and your video never leaves your device.