Generate subtitles and translate them on device.
Turn any video or audio into timed SRT, VTT or ASS subtitles — with a word-level editor and a second language, entirely in your browser.
Broadcast-grade subtitles. Zero uploads.
Whisper transcription, Marian translation and a real subtitle editor, all running locally.
100% private
Your footage never leaves the device. Decoding, transcription and translation all happen locally.
WebGPU accelerated
Transcription runs on your GPU when available, with a WebAssembly fallback.
Word-level timing
Timestamped Whisper models give per-word timings for tight cues and karaoke export.
Bilingual output
Translate into a second language and export both tracks stacked in either order.
From footage to subtitles.
- 01
Drop a video or audio file
Drag in MP4, WebM, MP3, WAV or M4A. It is decoded locally — nothing is uploaded.
- 02
Whisper writes the cues
Speech is transcribed in overlapping windows, then normalised to broadcast timing rules.
- 03
Edit, translate, export
Fix cues in the studio, add a translation, then download SRT, VTT, ASS, TXT or JSON.
About the subtitle generator
A free video-to-subtitle tool that listens to your audio with Whisper, writes timed cues, and can translate them into a second language — all inside the browser. It is built for creators, teachers, journalists and anyone captioning interviews, lectures, screen recordings or vlogs without handing raw footage to a cloud service.
How it works
The audio track is decoded with the Web Audio API and resampled to 16 kHz mono, then transcribed by a Whisper model running through Transformers.js. The file is walked in overlapping 30-second windows, so long recordings stream progress as they go and word-level timestamps stay accurate across window boundaries. Because the tool uses the timestamped Whisper builds, every cue also carries per-word timings, which drive the karaoke preview and the ASS karaoke export.
For translation, compact Marian (OPUS-MT) models are used, pivoting through English when the source and target have no direct model. Both the transcription and the translation models download once and are then cached, so a second run of the same language pair works offline.
Editing and quality
Generated cues are not set in stone. The studio pairs a live preview — with a broadcast-style subtitle overlay and a waveform timeline you can scrub — with a cue editor that supports inline text edits, splitting at the playhead, merging, duplicating, search & replace across both tracks, global time shifting, and full undo/redo. A quality panel flags every cue whose duration, reading speed, line length or overlap breaks normal subtitle conventions, and one click re-normalises the whole document.
Finished subtitles export as SRT, WebVTT, ASS, plain text or structured JSON, in the original language, the translation, or both stacked in either reading order.
Limits & requirements
The first run downloads model weights, which is the slowest step; afterwards they are cached. WebGPU (Chrome or Edge) makes transcription several times faster, and Safari or Firefox fall back to WebAssembly. Translation uses compact open models that are strong for general conversation and narration but should not be trusted for legal, medical or otherwise high-stakes wording. Very long recordings can exhaust memory on low-RAM devices; splitting the file is the workaround.
Privacy
Cloud captioning services receive your unedited footage and your scripts. Here nothing is uploaded: the video is decoded, transcribed and translated on your own machine, and the only files that leave the tab are the subtitles you choose to download.