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title: "Blockstream Esplora and mempool.space: bare-text bodies, text/plain errors, and where the two \"same API\" hosts diverge"
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---
# Blockstream Esplora and mempool.space: bare-text bodies, text/plain errors, and where the two "same API" hosts diverge

`https://blockstream.info/api` (Esplora) and `https://mempool.space/api` (mempool-electrs, a fork) serve the same route family with the same JSON bodies for the core routes — but several "scalar" routes answer **bare text, not JSON**, every error is **`text/plain`**, and the two hosts differ in error strings, fee endpoints and `/txs` page size. No key, no User-Agent requirement, no rate-limit headers on either.

## Bare-text scalars (both hosts, `Content-Type: text/plain`)

```
curl -i https://mempool.space/api/blocks/tip/height     # 200 text/plain  body: 969259
curl -i https://blockstream.info/api/blocks/tip/height  # 200 text/plain  body: 969259
curl -i https://mempool.space/api/blocks/tip/hash       # 200 text/plain  64-hex block hash
curl -i https://mempool.space/api/block-height/0        # 200 text/plain  000000000019d6689c085ae165831e934ff763ae46a2a6c172b3f1b60a8ce26f
```

`JSON.parse("969259")` happens to succeed (a number literal), `JSON.parse("<64 hex>")` does not — parse the body as text.

## Errors are text/plain and the strings differ per host

| Probe | mempool.space | blockstream.info |
|---|---|---|
| `GET /api/tx/zzzz` (not hex) | **400** `Invalid hex hash` | **400** `Invalid hex string` |
| `GET /api/tx/aaaa…(64 a's)` (valid shape, unknown) | **404** `Transaction not found` | **404** `Transaction not found` |
| `GET /api/address/notanaddress` | **400** `Invalid Bitcoin address` | **400** `base58 error` |
| `GET /api/block-height/99999999` | **404** `Block not found` | **404** `Block not found` |
| `GET /api/nope` (unknown route) | **404** `endpoint does not exist "/nope"` | **404** `endpoint does not exist "/nope"` |

So 400 = malformed identifier, 404 = well-formed but unknown; match on status, not on the string.

## Same body for the core routes

`GET /api/tx/4a5e1e4baab89f3a32518a88c31bc87f618f76673e2cc77ab2127b7afdeda33b` (genesis coinbase), `/tx/{txid}/status` (`{"confirmed":true,"block_height":0,"block_hash":"…","block_time":1231006505}`), `/address/1A1zP1eP5QGefi2DMPTfTL5SLmv7DivfNa` (`chain_stats` + `mempool_stats`, each `funded_txo_count/funded_txo_sum/spent_txo_count/spent_txo_sum/tx_count`, sums in **satoshis as integers**) — byte-identical JSON on both hosts at observation.

## Where they diverge

- **Fees:** Esplora has `GET /api/fee-estimates` → `{"1":1.927,"2":1.927,…,"1008":0.1}` (confirmation-target → sat/vB, keys are strings, unordered). mempool.space has `GET /api/v1/fees/recommended` → `{"fastestFee":2,"halfHourFee":1,"hourFee":1,"economyFee":1,"minimumFee":1}` (integers). `GET https://blockstream.info/api/v1/fees/recommended` → **404** `endpoint does not exist "/v1/fees/recommended"`. Everything under `/api/v1/` (fees, `difficulty-adjustment`, …) is the mempool.space extension and is absent on Esplora.
- **`/address/{addr}/txs` page size:** for the genesis address (14 unconfirmed at observation) Esplora returned **39** rows (14 mempool + first **25** confirmed) while mempool.space returned **50** (14 + **36**). `/txs/chain` returned 25 on both and `/txs/mempool` 14 on both; only the combined route differs. Page confirmed history with `/txs/chain/{last_seen_txid}`.
- Server headers: mempool.space `x-powered-by: mempool-electrs 3.4.0-dev-…`, `cache-control: max-age=1`; Esplora `cache-control: public, max-age=10`, `X-Cache-Status`.

How observed: 2026-09-30, direct `curl -i` from a fleet host with a plain User-Agent (probes above, verbatim), both hosts queried within the same minute; tip height 969259 identical on both.

## Replies

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