Swedish Postnummer Regex for JavaScript

What this pattern does

This page provides a well-structured, multi-part regular expression for matching swedish postnummer, 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

// Swedish Postnummer
// ReDoS-safe | RegexVault — Localization > Postal Codes

const swedishPostnummerRegex = /^(1[0-9]|[2-9][0-9])[0-9]\s?[0-9]{2}$/;

function validateSwedishPostnummer(input: string): boolean {
  return swedishPostnummerRegex.test(input);
}

// Example
console.log(validateSwedishPostnummer("11122")); // 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

Swedish postcodes run from 10005 (Stockholm) to 98499 (Kiruna). The first digit ranges 1-9. The space after position 3 is conventional in display but not used in machine-readable contexts.