The mempool (short for "memory pool") is where unconfirmed cryptocurrency transactions wait before miners pick them up and include them in the next block.
When you send Bitcoin or another cryptocurrency, your transaction does not instantly appear on the blockchain. Instead, it enters the mempool, a temporary holding area maintained by every node on the network. Each node has its own version of the mempool, though they largely overlap because transactions propagate quickly across the peer-to-peer network.
Miners select transactions from the mempool to fill the next block. They typically prioritize transactions with higher fees, because including those earns them more revenue. This creates a fee market: when the mempool is congested (lots of pending transactions), users must pay higher fees to get confirmed quickly. When traffic is low, even minimal fees will get your transaction through in the next block.
Mempool size is measured in virtual bytes (vB) or transaction count. A large mempool means the network is busy, and confirmation times will be longer for low-fee transactions. Watching the mempool gives you a real-time read on network demand.
If you are sending or receiving crypto, the mempool directly affects how long your transaction takes and how much you pay in fees. Traders use mempool data to gauge network congestion. A suddenly swelling mempool can indicate panic selling, exchange withdrawals, or high activity around a major event. For anyone building on Bitcoin, understanding the mempool is essential for setting appropriate fee levels.
The TerminalFeed dashboard shows live mempool data in the BTC Network panel, including current mempool size, fee estimates by priority, and recent block information pulled from mempool.space. For a full breakdown of how to read this data, check out Bitcoin Mempool: Network Health Explained.