Etherscan

Overview

Etherscan’s API provides Ethereum blockchain data — balances, transactions, tokens, contracts, gas prices, and logs. It powers countless explorer widgets and analytics dashboards.

⚠️ Breaking change (verified 2026-08): the legacy V1 endpoints are deprecated — requests return NOTOK: "You are using a deprecated V1 endpoint, switch to Etherscan API V2". Use the V2 API (https://api.etherscan.io/v2/api) per the migration guide.

Quick Start

V2 API (replace YOUR_KEY — note the /v2/api path):

curl "https://api.etherscan.io/v2/api?chainid=1&module=stats&action=ethsupply&apikey=YOUR_KEY"

{ "status": "1", "message": "OK", "result": "123594005058750000000000000" }

ETH balance of an address:

curl "https://api.etherscan.io/v2/api?chainid=1&module=account&action=balance&address=0xde0b295669a9fd93d5f28d9ec85e40f4cb697bae&apikey=YOUR_KEY"

Gas price:

curl "https://api.etherscan.io/v2/api?chainid=1&module=gastracker&action=gasoracle&apikey=YOUR_KEY"

Authentication

• Register at etherscan.io → free API key (in your account).
• Send it as the apikey query parameter.
• V2 requires chainid (1 = Ethereum mainnet) — the V2 API supports multiple chains.

Rate Limits & Notes

• Free tier: 1 request/second (5/sec with a key) + 100,000 requests/day — check the current limits.
• V1 endpoints return the NOTOK deprecation message (verified) — migrate to /v2/api.
• Modules: account (balances/transactions), stats (supply), gastracker, contract, token, logs…
• Other EVM chains are reachable via chainid on V2.

FAQ

Is Etherscan API free? Free tier with daily limits; a key raises them.

Why does my V1 request return NOTOK? V1 is deprecated — use https://api.etherscan.io/v2/api with chainid=1 (verified 2026-08).

Can I query other chains? Yes — V2 supports multiple EVM chains via the chainid parameter.