https://mempool.space/ is a comprehensive Bitcoin block explorer and mempool visualizer. It provides real-time updates and live transaction tracking, focusing on the ephemeral data from the mempool, which is the waiting area for unconfirmed transactions within a Bitcoin node. The site displays various statistics such as transaction fees, block times, and memory usage, helping users to estimate fees and transaction confirmation times. It’s an open-source project, emphasizing the transaction fee market and the multi-layer Bitcoin ecosystem