etherscan-api

Etherscan API

A way to access the etherscan.io api using promises. Fetch a diverse set of information about the blockchain.

Written in TypeScript, shipped as an ES module with bundled type declarations. Requires Node.js >= 20.

Mainnet

import { init } from 'etherscan-api';

const api = init('YourApiKey');
const balance = await api.account.balance('0xde0b295669a9fd93d5f28d9ec85e40f4cb697bae');
console.log(balance);

Example in the wild

Polymer3 based example

Zero dependencies / custom HTTP transport

This library has no runtime dependencies — requests use Node's built-in https module. If you need custom networking (a proxy, retries, a different agent), pass your own transport as the 4th argument to init. It receives the fully-qualified URL and must resolve with the parsed JSON body:

import { init } from 'etherscan-api';

// (url, { timeout, method, body }) => Promise<object>
// `method`/`body` are only set for the POST contract-verification endpoints;
// for read-only use you can ignore them.
async function request(url, { timeout, method = 'GET', body }) {
  const res = await fetch(url, {
    method,
    body,
    headers: body ? { 'Content-Type': 'application/x-www-form-urlencoded' } : undefined,
    signal: AbortSignal.timeout(timeout),
  });
  return res.json();
}

const api = init('apikey', null, 10000, request);

Security notes

The API key travels in the request URL. Etherscan requires apikey as a query parameter, so it is part of every request URL (and of POST request URLs). Treat full request URLs as secrets: do not log them, and be careful with proxies, APM tools, and access logs that capture URLs. A custom transport receives the URL containing the key — never write it to logs verbatim. (The library itself never puts the URL or key into thrown errors.)
The default transport refuses cleartext http://. Requests go to https://api.etherscan.io over TLS with certificate validation on. If a request somehow targets an http:// URL, the default transport rejects rather than sending the key unencrypted; pass { allowInsecure: true } in the transport options only if you deliberately need cleartext (e.g. a local test server).
The default transport caps the response body at 50 MB to guard against a memory-exhaustion response. Override with maxResponseBytes in the transport options if you expect larger payloads.

Selecting a chain (Etherscan V2 / multichain)

Etherscan deprecated the V1 API on 2025-08-15. This library now talks to a single base URL — https://api.etherscan.io/v2/api — and selects the network with a chainid query parameter. One API key works across all chains.

Pass a chain name (or a numeric chainid) as the second argument to init:

import { init } from 'etherscan-api';

// apikey, chain, timeout
const api = init('YourApiKey', 'sepolia', 3000);

Supported chain names:

Name	chainid
`mainnet` / `homestead` / `ethereum`	1
`sepolia`	11155111
`holesky`	17000
`arbitrum`	42161
`optimism`	10
`base`	8453
`polygon`	137
`bsc`	56
`avalanche`	43114

Any other chain is reachable by passing its numeric chainid directly, e.g. init('YourApiKey', 59144) for Linea.

Retired testnets (ropsten, rinkeby, kovan, goerli, morden, arbitrum_rinkeby, avalanche_fuji) have been removed and now throw an error with a helpful message — use sepolia or holesky instead.

Install

npm install etherscan-api --save

API Documentation

Full Api Docs

Development workflow

Source lives in ./src (TypeScript) and compiles to ./lib (ES modules + .d.ts).

npm run build - compiles src → lib with tsc
npm run typecheck - type-checks without emitting (replaces the old linter)
npm test - builds, then runs the fully mocked test suite (no API key required)
npm run test:live - runs the tests against the real Etherscan API
npm run docs - generates the API docs with TypeDoc
npm run preversion - type-check + changelog before tagging a release
npm run changelog - generates a changelog and pushes it