How to Read mempool.space: A Beginner's Tour of the Bitcoin Queue

Mempool.space is a free Bitcoin explorer that draws the network's waiting room as a row of blocks. The screen splits in two. On the left are projected blocks — transactions not yet confirmed, grouped into the blocks they are likely to land in. On the right are blocks already mined. The dotted line between them is the present moment, and everything flows right across it as new blocks arrive.

What the blocks on the left mean

Each projected block carries a fee rate in satoshis per virtual byte and a rough time: in about ten minutes, in about thirty. Read it as a queue with a price on every position. If the first block says 8 sat/vB, that is roughly what it costs to be in the next one. The colours are only a quick visual cue for how expensive a block is; the number is what you act on.

The figures along the top

Above the blocks sit the suggested tiers — high, medium, low and no priority — plus the size of the whole queue in virtual megabytes. A few vMB clears within hours. Dozens means a busy stretch. There is also a purging rate: the lowest fee nodes are still holding on to. Anything under it is being dropped rather than queued.

Finding your own transaction

Paste your transaction ID, which your wallet shows after you send, into the search box. The page reports the rate you paid, the size in virtual bytes, and which projected block you are sitting in. If your rate is below every projected block, you are behind the whole queue and waiting for it to clear.

A good first exercise: open it on a quiet evening, then again on a busy weekday afternoon, and compare. Seeing the queue and the prices move together makes the fee tiers stop feeling arbitrary. If the idea of a waiting room is new, start with what the mempool is.