A live, dark-mode visualizer of the Bitcoin blockchain. Mempossum surfaces what's happening on the network right now — the most recent blocks, the pending mempool, and the latest transactions — in a single Bloomberg-density dashboard.

How it works

Mempossum streams data from mempool.space's public REST + WebSocket APIs. On load the app hydrates the last several blocks and current mempool state, then opens a WebSocket subscription to the blocks, mempool-blocks, and live-2h-chart channels. New blocks, transactions, and fee updates push directly into the view as they arrive — no polling, no refresh button.

The web build runs entirely in your browser; nothing is logged or proxied through our servers.

What you're looking at

Recent Blocks (chart)

Each square is one mined block, positioned left-to-right oldest → newest. Square size scales with serialized size (MB); square color bands by size too — cool for small blocks, warm for full ones. The cyan and yellow bars overlaid on each block show transaction count and BTC value moved respectively, on a log Y-axis.

Recent Blocks (table)

Same blocks, expanded into a per-column readout: miner, time elapsed since the prior block, tx count, % full, total volume (XBT), total fees (XBT), size in bytes, fee rate in sat/vB, and the block hash. Click any row to open full block details with a link out to mempool.space.

Mempool (right side of Recent Blocks)

The two stacked bars show pending-but-unconfirmed transactions waiting to be mined — cyan for count, yellow for aggregate BTC value. The tx/sec rate above is a rolling intake measurement. Total fees, total size, and fee-per-byte give a quick read on how congested the next block will be.

Latest Transactions

The live tape of new unconfirmed transactions as they hit the mempool. Each row lists fee rate (sat/vB), size, value moved, and a truncated txid. Click any row for full details.

Mempool sparkline (bottom-left)

A two-hour history of mempool depth (transactions queued) and fee pressure. Useful for spotting fee-rate spikes before they show up on the main bars.

Live status dot (bottom-left corner)

Green = WebSocket connected and streaming. Amber = connecting or reconnecting. Red = disconnected; data is stale until reconnection succeeds.

BTC price (top-left)

Spot BTC/USD price, refreshed alongside the mempool feed.

XBT

The ISO 4217-style currency code for bitcoin. Identical to BTC; "XBT" is used in volume / fee columns to make the unit unambiguous in dense tabular contexts.

A note on accuracy

Mempool totals (volume, XBT-out) are estimates: mempool.space exposes aggregate vsize and fee data but not a directly-summed BTC-value field for the unconfirmed pool. Mempossum derives the XBT figure using the historical avg-tx-value × tx-count, with an uncertainty band visible on hover. Confirmed blocks use exact reported values.

Credits

Built and maintained by Logical Appeals, LLC. Live data courtesy of the mempool.space open-source project. Bitcoin is a public, decentralized network — Mempossum is just a window into it.

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