BTC - About Mempool and Expiry Time

Bitcoin transactions are not included in the next block immediately after they are broadcasted. These unconfirmed transactions are stored in a node's memory pool, commonly referred to as the "mempool".

The mempool acts as a temporary holding area for pending transactions. The duration for which transactions can stay in the mempool before they are dropped is known as the "mempool expiry time".

Default Mempool Expiry Time

The default mempool expiry time in Bitcoin is set to 2 weeks (14 days). This means that if a transaction remains unconfirmed for 14 days, it will be automatically removed from the mempool. After a transaction is removed (dropped) from the mempool, the UTXOs flagged on the transaction are freed up.

Tatum adheres to the default Bitcoin setting of a 2-week mempool expiry time.

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Find the default BTC GitHub mempool settings in the following link.

Good to Know

• Other node providers may use different mempool settings, either longer or shorter.
• Different Bitcoin explorers may fetch data from nodes with different settings.
• Once a UTXO used as input in a dropped transaction is freed up after 14 days, it can be used in a new transaction.
• A BTC transaction pending in the mempool may be sped up via RBF or CPFP
• A BTC transaction stuck in mempool cannot be "canceled".