Batch, hands-off
Drop several videos and get subtitle files. Speech recognition, translation and export run as one queue — per-video overrides, live progress, one-click retry.
00:00:01,000 → 00:00:04,200 · SRT · 24 fps
Every film deserves
perfect subtitles.
KenjaSub is an AI subtitle editor for Mac. Drop in any video — transcription runs entirely on your machine, translation happens in context with the AI model of your choice, and a frame-accurate studio polishes every line. SRT & WebVTT out.
REFINE
TC 00:00:24:12
転写も翻訳も、この Mac の中だけで完結する
Transcription and translation never leave your Mac
转写与翻译，全部在本机完成
— KenjaSub, the sage's subtitle studio
01
Three tabs, one workflow
From raw video to shipped bilingual subtitles without leaving the app — batch it, refine it, and bring your own model.
The subtitle studio
An mpv-based player opens MKV, WebM and AVI natively. Cue list and waveform stay in sync; drag timings, split and merge cues, shift the whole track, undo anything, export SRT or WebVTT.
Bring your own key
Any OpenAI-compatible provider — OpenAI, DeepSeek, OpenRouter, Ollama, LM Studio or your own endpoint. Keys live in your Mac's Keychain, never in plain files.
02
Built for people who care about lines
Not a cloud dashboard — a native Mac tool with an opinion about quality.
TRANSCRIPTION
On-device, always
Speech recognition runs with Apple's SpeechAnalyzer. Your audio never leaves the Mac — no uploads, no queue on someone else's server.
TRANSLATION
Reads the whole film
Lines are translated in context windows, so pronouns, tone and recurring names stay consistent from opening scene to credits. Six registers, from Literal to YouTube.
ASSISTANT
Chat with your subtitles
Retranslate a scene, shorten a line, fix a name — conversationally. "Ask before changes" stages every edit as a reviewable diff; automatic mode applies instantly with one-click undo.
TIMING
Frame-accurate control
Drag cue boundaries on the waveform, set in/out points at the playhead, type exact timecodes, split, merge, or shift the entire track. Full undo history included.
FORMATS
MKV in, SRT/VTT out
Native MKV, WebM and AVI playback via mpv. Bilingual SRT imports with automatic language detection — your existing translations come along.
QUALITY
Readable by design
Reading-speed and line-length checks keep subtitles comfortable on screen. When a source language or model answer looks wrong, KenjaSub stops and tells you.
03
Private by default
No accounts. No analytics. No tracking.
KenjaSub is private the way a hammer is private — it's a tool on your machine, not a service with a login. The rare data that moves, moves only when you choose an engine and only to the provider you configured.
✓Transcription: 100% on device
✓Local engine option: Apple Translation, on device
✓API keys: stored in Keychain only
✓Telemetry: none, ever
04
Questions, answered
Does KenjaSub upload my video or audio anywhere?
No. Speech transcription runs entirely on your Mac with Apple's SpeechAnalyzer — audio never leaves the device. When you choose an AI translation engine, subtitle text is sent only to the provider you configured, only when you run that engine.
Which AI models can it use for translation?
Any OpenAI-compatible provider: OpenAI, DeepSeek, OpenRouter, Ollama, LM Studio or your own endpoint — keys live in your Mac's Keychain. A fully local option using Apple's Translation framework is built in as well.
Which video and subtitle formats are supported?
The player opens MKV, WebM and AVI natively (mpv-based), plus standard MP4 and MOV. Subtitles import and export as SRT and WebVTT, including bilingual SRT files with automatic language detection.
Can I edit subtitle timings manually?
Yes — drag boundaries on the waveform, set in/out points at the playhead (⌘[ / ⌘]), type exact timecodes in the edit sheet, split and merge cues, shift the whole track earlier or later, and undo any of it.
What are the system requirements?
macOS 26 or later. On-device transcription and translation use Apple's neural frameworks, so Apple Silicon is recommended.
Does KenjaSub include AI model access?
No — AI features are strictly bring-your-own-key. You add a provider and key of your choice; KenjaSub never bundles or resells model access, which keeps your costs and your data under your control.