Blockchain
Mempool
The pool of unconfirmed transactions waiting to be included in a block.
Last Updated
2026-03-29
Related Concepts
What is Mempool?
The mempool (memory pool) is temporary storage where unconfirmed transactions wait before validators pick them up for inclusion in a block.
How does Mempool work?
- User broadcasts a signed transaction.
- It enters the mempool of network nodes.
- Validators select transactions prioritizing higher fees.
- Once included in a block, the transaction is removed from the mempool.
Why does Mempool matter?
It lets users estimate fees and predict confirmation times. It also enables MEV bots scan pending transactions and reorder them for profit.
Key features of Mempool
- Public and observable by all nodes
- Higher-fee transactions get priority
- Size fluctuates with network congestion
- Foundation for MEV opportunities
Examples of Mempool
During high activity the mempool can hold 10,000+ pending transactions. Users can watch their transaction sitting "pending" in a block explorer until a validator picks it up.