priority fee

The priority fee — informally the 'tip' — is the per-gas bonus a sender offers the block proposer on top of the mandatory base fee, to encourage prompt inclusion. Where the base fee is burned and benefits no one in particular, the priority fee is the one part of the gas payment that actually lands in the proposer's pocket. It is how you say 'please pick my transaction first' when blockspace is contested.

In an EIP-1559 (type-2) transaction the sender sets two numbers: maxPriorityFeePerGas, the most they will tip, and maxFeePerGas, the absolute most they will pay per gas in total. The proposer actually receives the smaller of the requested tip and whatever room is left after the base fee — formally min(maxPriorityFeePerGas, maxFeePerGas − baseFee). So if the base fee unexpectedly rose toward your maxFeePerGas, your effective tip shrinks automatically, protecting you from overpaying while keeping the transaction valid.

Because proposers are profit-seeking and order transactions to maximize revenue, the priority fee is the lever ordinary users pull to compete for position within a block. Under normal conditions a tip of a gwei or two is plenty; during high-demand events — a hot NFT mint, a liquidation cascade — tips spike as bots and users outbid each other for early placement. This is where the priority fee blurs into MEV: searchers will pay very large tips (or bribe builders directly) to land profitable transactions in exactly the right slot.

It is worth keeping the two fees mentally separate. The base fee answers 'is there room in recent blocks?' and is set by the protocol; the priority fee answers 'how badly do I want to be early?' and is set by you. Setting a near-zero tip on a quiet chain often still confirms; setting a generous one during congestion is what jumps the queue.