Altcoins are any cryptocurrency other than Bitcoin. Alternative coins is the short name for this cryptocurrency. Altcoins are all the other thousands of coins and tokens, such as Ethereum, Dogecoin Litecoin Tether and more. Altcoins are sometimes defined as excluding Bitcoin and Ethereum. However, for the purposes of general discussion, altcoins can be thought of as "the rest of the crypto-world."

Tens of thousands altcoins exist. The majority of altcoins were created after Bitcoin to test out new features or ideas.