ってCasual quotation

って (a contracted form of と) is a casual quoting particle used to mark direct or indirect speech, thoughts, feelings, or to introduce a topic casually. For example, 行くって言っていた means '[They] were saying [they] will go.' といってもいい combines と with 言う and いい, meaning 'You/one could say' (literally: 'It's fine even if one says...').

って (a contracted form of と) is a casual quoting particle used to mark direct or indirect speech, thoughts, feelings, or to introduce a topic. んだって, which combines って with the explanatory ん・の, is used to express 'I heard' or 'He/she/they said.' While って can follow any word, んだって requires な before な-Adjectives or nouns.

と and って are quoting particles marking direct or indirect speech, thoughts, or feelings. For example, 行くと言っていた and 行くって言っていた both mean '[They] were saying [they] will go.' The difference is that って is used mainly in casual conversation, while と is used in speech or writing. って can also casually introduce a topic, like 日本っていいよね ('Japan is great, isn't it?'), which と cannot.