Ethereum Checksummed Address (EIP-55) Regex for JavaScript

What this pattern does

This page provides a well-structured, multi-part regular expression for matching ethereum checksummed address (eip-55), ported and verified for JavaScript. Financial data validation has zero tolerance for false negatives — a missed invalid entry can corrupt downstream calculations. The snippet below is ready to drop into your JavaScript project — whether you're validating in an Express middleware, a Next.js API route, or a client-side form.

Javascript Implementation

// Ethereum Checksummed Address (EIP-55)
// ReDoS-safe | RegexVault — Finance > Crypto

const ethereumChecksummedAddressEip55Regex = /^0x(?:[0-9A-F]{40}|[0-9a-f]{40}|(?:[0-9a-fA-F]{40}))$/;

function validateEthereumChecksummedAddressEip55(input: string): boolean {
  return ethereumChecksummedAddressEip55Regex.test(input);
}

// Example
console.log(validateEthereumChecksummedAddressEip55("0xAb8483F64d9C6d1EcF9b849Ae677dD3315835cb2")); // true

Test Cases

When to use this pattern

This pattern is drawn from the Finance > Crypto category and carries a ReDoS-safe certification. That matters for JavaScript developers because especially critical in long-running Node.js event loops where a ReDoS vulnerability can block the entire process. RegexVault audits patterns against known backtracking attack vectors, ensuring you have the necessary context before using this regex in a high-stakes production environment.

Common Pitfalls

Technical Notes

EIP-55 checksum embeds a SHA3 hash of the lowercase address in the casing of the hex letters. A correctly checksummed address has mixed case. Regex alone cannot verify EIP-55 — use a library. This pattern just validates the format.