Look up words
without leaving the video.
KOTO shows definitions, readings, and word information beside your subtitles. Import the dictionaries you use and look up words offline.
A video playerbuilt forlanguage learning.
Learn languages from the things you actually want to watch. Interactive subtitles, lookup, mining, and SRS review. Koto is available now and local-first.
Watch a video.
Look up any word.
Hover over a subtitle to see its definition. Click to pin it.
Press E to save the word and its sentence.
Silent sample · 18 seconds
IN THIS SENTENCE
0:00 / 0:18
Play, pause, or scrub the sample. Hover or tap a subtitle word to
look it up.Interactive preview
Look up words
Save a word
with its context.
Press E to save a word with its sentence, screenshot, and subtitle-timed audio when available. Your vocabulary stays in a local library.
Review in KOTO.
Or export to Anki.
Built-in spaced repetition schedules your vocabulary for review. Export cards with media to Anki, or send them directly with AnkiConnect.
ReviewSample card
木漏れ日
こもれび
Sunlight filtering through the trees.
What does this word mean?
Sample review — no progress is stored
Smart reviews.
Review only what you’re watching.
Koto automatically freezes cards that aren’t showing up in your current immersion. They’re still saved, but put on pause—drastically cutting daily review time so you can focus on making what you watch comprehensible, reaching fluency faster where learning rare words becomes easy anyway.
Turn what you watch
into what you remember.
Look up a word, save its context, and review it later. The current core works locally without an account; learning data stays on-device by default.
Works offline
After installing your dictionaries.Local storage
Vocabulary, media, and review history.Review in one place
Study saved words without switching apps.Choose how you learn.
Start with Koto. Kiwami is coming soon.
Koto
Available nowLocal video playback, interactive subtitles, dictionary lookup, vocabulary mining, smart reviews, and spaced repetition on your device.
Get Koto ↗Koto Kiwami
Coming soonAI recommendations, sync, and more in the future.
Questions
What can I watch with KOTO?
Your own video files, including MKV, MP4, and WebM. Add SRT, ASS/SSA, or WebVTT subtitles for interactive word lookup. KOTO is a player; films, shows, and subtitles are yours to bring.
Is it just for Japanese?
Japanese is at the heart of KOTO, with word segmentation and readings. English and Korean are also supported. You can import compatible Yomitan dictionaries for additional languages.
Do I need an internet connection?
Once KOTO and your dictionaries are installed, local video playback, dictionary lookup, sentence mining, and review work offline. Online media and dictionary downloads need a connection.
Can I use my existing Anki setup?
Koto includes spaced-repetition review with Smart Reviews, which automatically freeze cards not appearing in your current immersion to keep daily reviews fast and focused. If you use Anki, you can enable export or AnkiConnect in Settings. Your saved words remain in Koto.
Which platforms are supported?
Koto is available for Windows, macOS (Apple Silicon), and Linux. Download the latest installer for your system from the downloads section or GitHub Releases.
Get Koto.
Available for Windows, macOS, and Linux.
Download Koto