SSH Public Key Regex for JavaScript

What this pattern does

This page provides a comprehensive, battle-tested regular expression for matching ssh public key, ported and verified for JavaScript. In security-sensitive code, using an unverified regex can open the door to both false positives and denial-of-service attacks. 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

// SSH Public Key
// ReDoS-safe | RegexVault — Security > Certificates & PKI

const sshPublicKeyRegex = /^(ssh-rsa|ssh-ed25519|ssh-ecdsa|ecdsa-sha2-nistp256|ecdsa-sha2-nistp384|ecdsa-sha2-nistp521|sk-ssh-ed25519@openssh\.com|sk-ecdsa-sha2-nistp256@openssh\.com)\s+([A-Za-z0-9+\/]{20,800}(?:={0,3}))(?:\s+(.+))?$/;

function validateSshPublicKey(input: string): boolean {
  return sshPublicKeyRegex.test(input);
}

// Example
console.log(validateSshPublicKey("ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIOMqqnkVzrm0SdG6UOoqKLsabgH5C9okWi0dh2l9GKJl user@host")); // true

Test Cases

When to use this pattern

This pattern is drawn from the Security > Certificates & PKI 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

Capture groups: 1=key type, 2=base64 key material, 3=comment (optional, usually user@host). Supported types: RSA (deprecated), Ed25519 (preferred), ECDSA (nistp256/384/521), SK (FIDO2 hardware key variants). Prefer Ed25519 for new SSH keys.