Mint authority

Mint authority is a permission stored in a Solana token's mint. The address that holds it can create any number of new tokens at any moment. The permission can be permanently disabled (revoked) by setting it to none, and that change cannot be undone. On EVM networks the equivalent is an owner-only mint function in the contract code.

In a memecoin an active mint authority means the supply is not really fixed. The creator can print billions of tokens and sell them into the pool, pushing the price close to zero, and market cap and FDV stop meaning anything. Tokens from major launchpads usually start with mint authority disabled. Tokens created by hand need to be checked separately.