Used in affirmative, negative, and interrogative sentences to mean 'any place' or 'no matter where'. Often implies that a condition holds in all locations.
このカードは世界中どこでも使えます。
You can use this card anywhere in the world.
彼はどこでも寝られる。
He can sleep anywhere.
どこでも simply means 'anywhere' in terms of location, while どこまでも adds the sense of going or continuing without any limit.
どこでも means 'anywhere, no matter where' emphasizing lack of restriction, while どこにも focuses on existence or non-existence across all places.
どこでも means 'anywhere/everywhere' in affirmative contexts, the opposite of どこにもない which denies existence in any place.
anywhere door
Compound of どこ (where) + でも (even, also). The combination yields the meaning 'anywhere' or 'no matter where'.