UK Postcode (Full Format) Regex for JavaScript

What this pattern does

This page provides a comprehensive, battle-tested regular expression for matching uk postcode (full format), ported and verified for JavaScript. A rigorously tested regex reduces debugging time and protects your application from edge-case failures. 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

// UK Postcode (Full Format)
// ReDoS-safe | RegexVault — Localization > Postal Codes

const ukPostcodeFullFormatRegex = /^(?:GIR\s*0AA$|[A-PR-UWYZ](?:[A-HK-Y][0-9][0-9A-HJKMNPR-VWY]?|[0-9][0-9A-HJKMNPR-VWY]?)\s[0-9][ABD-HJLNP-UW-Z]{2})$/i;

function validateUkPostcodeFullFormat(input: string): boolean {
  return ukPostcodeFullFormatRegex.test(input);
}

// Example
console.log(validateUkPostcodeFullFormat("SW1A 1AA")); // true

Test Cases

When to use this pattern

This pattern is drawn from the Localization > Postal Codes 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

Structure: area (1-2 letters) + district (1-2 alphanumeric) + space + sector (1 digit) + unit (2 letters). The inward code letters exclude C, I, K, M, O, V. GIR 0AA is the only postcode without a space.