About Subtitle Edit Online
A fast subtitle editor for the browser – independent, free and without uploads.
Who is behind it?
Subtitle Edit Online is a web tool by Answer the Web, operated by LLG 369 LLC. We are not affiliated with the open-source project Subtitle Edit or its author Nikolaj Lynge Olsson. You can find the official software at nikse.dk/subtitleedit.
How it works
The editor is plain JavaScript. Subtitle files are read with our own parsers for SRT, WebVTT, ASS/SSA, SBV and MicroDVD, and the character encoding is detected automatically. Your browser plays videos straight from your disk; for the waveform the audio track is decoded locally with the Web Audio API. None of this leaves your device.
Auto subtitles use OpenAI’s Whisper via transformers.js and ONNX Runtime – on the graphics card with WebGPU, otherwise on the CPU via WebAssembly. Words with timestamps are grouped into subtitle lines: at most two lines of 42 characters, at most six seconds, with a new line after pauses and sentence ends.
Checking rules
The error check follows common guidelines of major streaming services: at most two lines of 42 characters, 0.7 to 7 seconds on screen, no overlaps, and reading speed against a selectable limit (15, 17, 20 or 25 characters per second).
Limits
OCR for image subtitles (Blu-ray SUP, DVD VobSub), the spectrogram, machine translation and the 300+ special formats of the desktop app are not available online. Very large videos (over 1.5 GB) may need too much memory for the waveform.
Contact
Questions and feedback: subtitleedit@llg.marketing.