Cryptocurrency — entry 043 of 53
Mempool
mempool.space runs an open-source Bitcoin block explorer and fee-estimation API — originally forked from Blockstream's Esplora backend and now maintained as its own mempool/electrs fork — answering over REST and WebSocket with no signup needed to read blocks, transactions, addresses, and the Lightning Network graph. It's free for public use, with a paid Mempool Enterprise tier adding unmetered access and multi-datacenter SLAs for heavier commercial traffic.
mempool.space runs an open-source Bitcoin block explorer and fee-estimation service, forked from Blockstream's Esplora backend and extended with its own fee, mining-pool, and Lightning Network endpoints — all keyless JSON (and some plain-text) over a single /api path.
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<a href="https://greatapis.com/api/mempool/"><img src="https://greatapis.com/badge/mempool.svg" alt="Scored 91 on greatapis.com"></a>Auth quickstart
- No API key required — requests are public and keyless. There's no published fixed rate ceiling for the free public instance; the docs simply warn that exceeding an unpublished threshold returns a 429, and suggest an Enterprise sponsorship (or self-hosting your own mempool/electrs instance) if you need guaranteed higher throughput.
Your key is stored only in this browser (localStorage) and sent directly to the API — never to greatapis.
Get the current recommended transaction fees
GEThttps://mempool.space/api/v1/fees/recommended
{"fastestFee":1,"halfHourFee":1,"hourFee":1,"economyFee":1,"minimumFee":1}Try it
Developer reference
https://mempool.space/apiEnforced (exceeding it returns HTTP 429); exact numeric threshold is not publicly disclosed, though a paid enterprise sponsorship raises it
- GET/blocks/tip/height
- GET/v1/fees/recommended
- GET/tx/{txid}
Gotchas & limits
- Esplora-inherited routes sit directly under
/api/...(e.g./api/blocks/tip/height) while mempool.space's own fee-estimation additions sit under/api/v1/...(e.g./api/v1/fees/recommended) — same host, two versioning conventions on one base path. - Several endpoints return
text/plain, not JSON: a liveGET /api/blocks/tip/heightcame back200 text/plainwith a bare numeric body (959656), no braces to parse. - Fee values are already-rounded sat/vB integers for display, not high-precision floats — don't expect fractional sat/vB estimates.
- There's no documented fixed rate limit; the docs only promise a 429 once you cross an unpublished threshold and point to an Enterprise tier for higher, contracted limits.