Blockchain — entry 002 of 11
Blockscout
Blockscout is the open-source, EVM-compatible block explorer behind dozens of public chain explorers (Ethereum mainnet, its L2s, and more), and its REST v2 API exposes the same block, address, token, and transaction data that powers those explorer UIs. No signup or API key is required for the per-instance hosted public REST API, though anonymous callers are rate-limited per endpoint (confirmed live: `x-ratelimit-limit` varies by route, e.g. 180 on an address lookup vs. 10 on `/stats`); docs.blockscout.com also flags this per-instance API for deprecation in favor of a separate, paid, API-key-gated multichain "PRO API," though the free per-instance API this entry tracks was still live and keyless as of this run's probe. Every response is JSON.
Blockscout is the open-source block explorer behind dozens of public chain explorers, and its REST v2 API exposes the same address, transaction, and stats data that powers the explorer UI. A live GET to `eth.blockscout.com/api/v2/addresses/{address}` in this run returned full real account data — balance, contract-verification status, resolved ENS name — with zero credentials, and `access-control-allow-origin: *` on every call. `eth.blockscout.com` is documented here as the Ethereum-mainnet instance; Blockscout also runs a separate hosted instance per chain (L2s, sidechains, and more) behind the same API shape.
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<a href="https://greatapis.com/api/blockscout/"><img src="https://greatapis.com/badge/blockscout.svg" alt="Scored 88 on greatapis.com"></a>Auth quickstart
- No API key or signup required for this per-instance public REST API — every probe in this run answered with no auth header sent at all. Anonymous callers are rate-limited per endpoint (see gotchas); a `bypass-429-option: temporary_token` response header points at a captcha-gated temporary token for higher throughput, and Blockscout also sells a separate, paid, multichain "PRO API" (dev.blockscout.com) with its own API keys and higher limits — not required for the reads this quickstart covers.
Your key is stored only in this browser (localStorage) and sent directly to the API — never to greatapis.
Look up an address
GEThttps://eth.blockscout.com/api/v2/addresses/0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045
{"hash":"0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045","ens_domain_name":"vitalik.eth","coin_balance":"6632273951167510873","exchange_rate":"1880.27","is_contract":true,"is_verified":true,"is_scam":false,"implementations":[{"address_hash":"0x5A7FC11397E9a8AD41BF10bf13F22B0a63f96f6d","name":"AmbireAccount7702"}],"has_tokens":true,"has_token_transfers":true,"reputation":"ok"}Developer reference
https://eth.blockscout.com/api/v2Gotchas & limits
- The `x-ratelimit-limit`/`x-ratelimit-remaining`/`x-ratelimit-reset` response headers do not carry one fixed number for the whole API — a live probe in this run got `x-ratelimit-limit: 180` on `/addresses/{hash}` but `x-ratelimit-limit: 10` on `/stats`, confirming the limit is set per endpoint, not per instance. docs.blockscout.com's own requests-and-limits page separately documents a default "no API key (by IP)" limit of 3 requests/minute for the legacy per-instance model — that page's stated number and this run's observed headers don't agree, so no single `rateLimit` figure is trustworthy enough to state as fact; treat the headers on your own calls as the source of truth.
- docs.blockscout.com carries an explicit notice that "PER INSTANCE API WILL BE DEPRECATED JULY 1" in favor of the paid, multichain PRO API (5 RPS on its free tier, API-key gated) — yet this run's live probe against `eth.blockscout.com/api/v2/*` still returned normal 200s with no key, so the per-instance API this quickstart documents is still live in practice even though its long-term future is explicitly in question.
- A syntactically valid but unused address doesn't 404 — a live GET to a made-up-but-valid 40-hex-char address returned HTTP 200 with `"coin_balance":null,"exchange_rate":"1880.27","is_contract":false` and most other fields `null`, not an error. A genuinely malformed address (wrong length/characters) is what actually 404s/422s: a live GET to `/addresses/not-a-real-address` returned HTTP 422 `{"errors":[{"title":"Invalid value",...,"detail":"Invalid format. Expected ~r/^0x([A-Fa-f0-9]{40})$/"}]}`, and a made-up transaction hash in the correct format returned a plain HTTP 404 `{"message":"Not found"}`.
- The entry's `url` (dev.blockscout.com) is Blockscout's PRO API developer portal, not the REST API reference — the actual endpoint docs live at docs.blockscout.com/devs/apis/rest, confirmed live 200 in this run and recorded as this entry's `docsUrl`.