AxTongue

AxTongue hosts user-submitted dynamic bilingual captions for YouTube videos.

Corresponding phrases from both languages light up as the video goes along. This allows you to understand a language you don't know in real time. To immerse yourself in it without the years of struggle it would otherwise take.

You can start right away, without knowing a single word of the language you want to learn, and you can keep going until you're confident you can understand the language in the wild—as soon as there are enough translations. If you could add translations yourself, or donate so I can commission translations, it would be very helpful.