How it works
Drop. Pick. Post.
Here's what happens inside.
OpaCaptions turns speech into styled, word-by-word captions in one window, entirely on your PC. Here's each step, what your computer needs, and why your video never has to leave it.
OpaCaptionsInterface preview: OpaCaptions is in early access. A 30-second clip takes about 10 seconds on an ordinary laptop in Fast mode.
Step by step
Five steps.
All of them on your PC.
- 1
Drop in a file
Drag any video or audio file into the window: MP4, MOV, MKV, WEBM, MP3, WAV or M4A, up to 2 GB. Vertical, landscape and audio-only all work.
The file is read straight from your drive. Nothing is copied anywhere else.
- 2
Transcribe
OpenAI's open-source Whisper model listens and writes down every word with its exact timing. Pick Fast, Balanced or Best accuracy, and the spoken language, or let it detect the language for you.
Whisper runs on your own processor. No graphics card, no cloud.
- 3
Style
Choose a caption style and see it on your video straight away; on Pro, tweak its font, colours, size and position. One switch turns any of the 17 languages into English captions.
The preview is live; nothing is rendered until you export.
- 4
Review
Read the transcript beside the video. Every word lights up as it's spoken, clicking a line jumps the video there, and search finds any moment.
Your transcript stays a file on your PC, not a record on someone's server.
- 5
Export
Get an MP4 with the captions burned in, ready for TikTok, Reels and Shorts, plus SRT and VTT subtitle files and a TXT transcript, saved to your folder.
Rendering uses ffmpeg on your PC. Upload counter: still 0 bytes.
Requirements
What your PC needs.
Probably what you have.
Speed and accuracy
Fast when you need it.
Careful when it counts.
On the 8th-generation Intel Core i5 laptop we build on, a 24-second clip is captioned and rendered in about 9 seconds in Fast mode. Faster PCs simply finish sooner.
| Mode | Best for | Model download |
|---|---|---|
| Fast | Clear speech, quick social clips | about 150 MB |
| Balanced | Most videos and podcasts | about 0.5 GB |
| Best | Accents, background noise and technical words | about 1.6 GB |
Balanced and Best take longer than Fast, in exchange for catching more words in difficult audio.
Works offline
Switch on airplane mode.
It keeps working.
After the one-time model download and licence activation, OpaCaptions needs no internet at all. That's the simplest proof that your footage never leaves your PC: unplug the network and caption a video. Read more in our privacy policy, or see what stays on your PC.