字幕を生成し、 端末内で翻訳。
動画や音声を、タイミング付きの SRT・VTT・ASS 字幕に。単語単位の編集と第二言語への翻訳まで、すべてブラウザ内で完結します。
放送品質の字幕を、アップロードなしで。
Whisper による文字起こし、Marian 翻訳、本格的な字幕エディタをすべてローカルで実行。
100% プライベート
素材が端末から出ることはありません。デコード・文字起こし・翻訳はすべてローカルです。
WebGPU で高速化
利用可能なら GPU で文字起こしを実行し、WebAssembly にフォールバックします。
単語単位のタイミング
タイムスタンプ対応の Whisper モデルが単語ごとの時間を返し、詰まった字幕とカラオケ書き出しを実現します。
バイリンガル出力
第二言語へ翻訳し、2 つのトラックを好きな順序で重ねて書き出せます。
素材から字幕へ。
- 01
動画か音声をドロップ
MP4・WebM・MP3・WAV・M4A をドラッグ。ローカルでデコードされ、送信はされません。
- 02
Whisper が字幕を作成
音声は重なり合うウィンドウで文字起こしされ、放送基準のタイミングに整えられます。
- 03
編集・翻訳・書き出し
スタジオで字幕を修正し、翻訳を加えて、SRT・VTT・ASS・TXT・JSON をダウンロード。
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.