Unconfirmed transaction

Once a wallet signs and broadcasts a transaction, nodes check it and keep it in their mempools until a miner or validator includes it in a block. During that window the explorer shows it as pending or unconfirmed. Most transactions wait seconds or minutes, but when blocks are full, those paying low fees can sit for hours or days.

Users have tools to rescue stuck transactions. On Bitcoin, replace-by-fee lets the sender rebroadcast with a higher fee, and child pays for parent lets the recipient spend the pending output with a high-fee transaction. On Ethereum, a wallet can send a new transaction with the same nonce and a higher fee to speed it up or replace it with a zero-value transfer to cancel it.

An unconfirmed payment is not final and should not be treated as received for anything valuable. Nodes may drop it after a while if fees stay low, and on Bitcoin the sender can replace it with a conflicting transaction. On account-based chains, one stuck transaction blocks all later ones from the same account until it clears.