Oops, I accidentally learned Japanese.

You read things in your browser every day. This extension puts Japanese words into them gradually until you learn them all. A word you are ready for takes the place of its English counterpart. Rest your pointer on it for half a second and it turns gold: that is you confirming that you've read it. Click the word instead and it tells you what it means, which counts as not knowing it yet. How much Japanese a page shows is worked out from what you can already read. Words you find hard come back faster. Words you know stay on the page, so what you read drifts towards Japanese rather than staying an English page with decorations in it. Pronunciation help fades one sound at a time, so it never disappears before you are ready for it to. It runs on your machine. No page you visit or data is sent anywhere. Making an account is optional and exists only to carry your progress to your other browsers. As of today 2,019 words and 1,018 kanji, N5 through N1. Support us by purchasing a license to sync between devices, which will make the extension better with time and help pay for infrastructure costs. You can always keep everything local; import, or export your progress for free forever.