also: なくてもよい
need not; don't have to
Attaches to the negative stem of a verb or adjective to express lack of obligation or necessity. Very common in everyday speech.
You don't have to work overtime today.
You don't need to hurry so much.
need not have; need not exist
Used when saying that something does not need to be present or exist. Often appears in conditional or hypothetical contexts.
See also: ない
You don't need any special tools.
You don't need a reason; let's just give it a try.
なくてもいい means something is not necessary or optional, the opposite of 無くてはいけない which insists it is required.
無くてはならない means something is essential and 'must exist', while なくてもいい means it's fine even without it—learners often mix up the opposite meanings due to their similar 〜なくて〜 form.
Kanji spelling using 無い and 良い; more formal or literary feel.
Kana spelling with the more formal よい ending.
Formed from the negative stem of a verb/adjective + ても (even if) + いい (good), literally 'it's good even if not...'. The kanji spelling 無くても良い uses 無い (not exist) and 良い (good).