mempool

Mempool (mempool.space) is an open-source Bitcoin block explorer and mempool visualizer. Its core business is presenting the Bitcoin network's pending transaction queue, fee market, and mined blocks in an intuitive, visual interface. Users can search any transaction ID to see its confirmation status, fee rate, size, inputs/outputs, and position in the fee market.

The project's core value proposition is making Bitcoin's mempool—the set of unconfirmed transactions nodes hold—legible to ordinary users. It visualizes transactions as projected blocks, with higher-fee transactions in the first block and lower-fee ones deeper down, making the block-space market obvious at a glance. The software is AGPL-licensed and self-hostable, allowing users to run their own instance against their own node, which addresses privacy concerns with public explorers.

The market pain point it solves: users previously had no easy way to understand when a transaction might confirm or what fee to set. Mempool provides real-time fee rate suggestions, shows the minimum fee threshold when the mempool is full (default 300MB memory limit), and offers tools like block audits that compare expected vs. actual block contents to detect miner behavior anomalies.

In the past six months (2026-03-12 to 2026-09-12), the project continued operating its public instance and maintaining the open-source codebase. Notably, in October 2024, the addition of transaction filters for Ordinals and Runes sparked community debate about how Bitcoin services should present non-monetary blockchain uses—a controversy that remained part of the project's context within the past two years.