Bitcoin Mempool Congestion: How Fees Affect Confirmation Time

The Bitcoin mempool is where pending transactions wait before miners include them in a block. It's not one global waiting room, but rather each node keeps its own view of valid, unconfirmed transactions.

When a wallet broadcasts a signed transaction, peers can verify and relay it through the network. The TXID identifies that transaction until a miner includes it in a block, making it confirmed.

The main factor affecting confirmation time is how a transaction's effective fee rate compares with others competing for limited blockspace. Mempool congestion, vsize, unconfirmed parents, package feerate, relay policy, miner policy, and propagation also play a role.