TL;DR
SPL tokens are the standard fungible token format on Solana, created using the Solana Program Library — equivalent to ERC-20 tokens on Ethereum.
The SPL Token program is a smart contract deployed on Solana that handles token creation, transfers, and management. When someone launches a memecoin on Pump.fun or creates a governance token, they’re creating an SPL token. Each token has a unique mint address, and users hold tokens in Associated Token Accounts (ATAs) linked to their wallet. Unlike Ethereum where each token deploys its own contract, all SPL tokens share the same on-chain program.
Every SPL token has a mint authority (can create new supply), a freeze authority (can freeze accounts), decimals (usually 6 or 9 on Solana vs 18 on Ethereum), and a total supply. When evaluating token safety, checking whether mint and freeze authorities are revoked is critical — an active mint authority means the creator can inflate supply at any time.
The original SPL Token program is being supplemented by Token-2022 (Token Extensions), which adds features like transfer fees, confidential transfers, and metadata directly on the token. Most existing tokens still use the original program, but new projects increasingly adopt Token-2022 for its additional capabilities.