What is comprehensible input?

Comprehensible input is language you can mostly understand even though it's a little beyond your current level — the idea, popularised by linguist Stephen Krashen, that we acquire language by understanding messages, not by memorising rules.

The practical challenge is staying in that sweet spot: material that's too easy doesn't stretch you, while material that's too hard becomes noise. Real native content with captions lets you push slightly past your level while keeping a safety net for the words you don't yet know.

Echoling is built around authentic input: you bring real YouTube videos at the level you choose, and the app breaks them into sentence-sized pieces you can replay, read, and practise until they become comprehensible — then move on to harder material.