Sensim — Learn, without really trying. per Justin

Sensim replaces English words on every page you browse with their equivalent
in your chosen language — but only words you've already proven you know.

How it works:
- 3 new words unlock every day
- Review them in your daily flashcard deck (under 2 minutes)
- Get a word right 3 out of 4 days and it graduates to your browser
- Graduated words appear on every page you visit as passive reinforcement
- Hover any substituted word to see its English meaning
- If you keep hovering a word too often, it returns to your deck automatically

1,000-day journey. 3,000 words. 100 languages.

Supports Spanish, French, German, Japanese, Korean, Chinese, Arabic, Hindi,
Russian, Portuguese, Italian, Turkish, Persian, Swahili, and 85 more —
including Cherokee, Nahuatl, Welsh, Hawaiian, Tibetan, and other indigenous
and endangered languages.

All progress stored locally. No account required. No ads. Ever.