The mempool
The Bitcoin mempool is the set of valid transactions a node has received but that no block has included yet.
As of block 971,630 (15 Oct 2026, 23:06 UTC), 55,163 transactions are waiting, about 30 blocks' worth.
A waiting room for transactions that have been broadcast but not yet put in a block. When it is crowded, people outbid each other with fees; when it is quiet, the minimum fee gets you in.
Is there one mempool?
No. Every node keeps its own, and they differ a little: a node may have missed a transaction or set its own limits. Ours is the one this site shows. Miners build their next block from theirs.
What happens to a transaction that waits too long?
Bitcoin Core drops it after two weeks by default, or sooner if the mempool fills its memory limit and its fee rate is among the lowest. The coins never left the wallet, so it can be sent again with a higher fee.
Why does the mempool fill up?
Blocks have a fixed size and arrive about every 10 minutes. When people send more than fits, the rest waits, and the fee rate needed to get into the next block rises until the queue clears.
Sources
Updated 10 Oct 2026
Related words
Something look wrong? Tell us