validation
UK Postcode Regex Pattern
Validates UK postcodes in the common formats (SW1A 1AA, M1 1AE, etc.). Case-insensitive by flag. Covers ~99% of valid postcodes but doesn't check that the specific postcode exists.
/^[A-Z]{1,2}\d[A-Z\d]?\s*\d[A-Z]{2}$/i What each part matches
^[A-Z]{1,2} — 1-2 letter area code\d — district digit[A-Z\d]? — optional sub-district char (letter or digit)\s* — optional space\d[A-Z]{2}$ — sector digit + 2 unit letters✓ These match
- SW1A 1AA
- M1 1AE
- B33 8TH
- CR2 6XH
✗ These don't
- 1SW A1AA
- SW1
- SW1A1A
- 12345
Use in your code
JavaScript
const re = /^[A-Z]{1,2}\d[A-Z\d]?\s*\d[A-Z]{2}$/i;
re.test(input); // → true or falsePython
import re
re.fullmatch(r"^[A-Z]{1,2}\d[A-Z\d]?\s*\d[A-Z]{2}$", input)PHP (PCRE)
preg_match('/^[A-Z]{1,2}\d[A-Z\d]?\s*\d[A-Z]{2}$/i', $input);Go
re := regexp.MustCompile(`^[A-Z]{1,2}\d[A-Z\d]?\s*\d[A-Z]{2}$`)
re.MatchString(input)FAQ
Does this uk postcode regex work in JavaScript?
Yes. Every pattern in the Utilko regex library is tested to work in JavaScript RegExp, PCRE (PHP, Nginx), and Python `re`. Where flavor matters (lookbehind, named groups), the pattern page flags it.
How do I use this pattern?
Copy the pattern from the code block above. In JavaScript:
new RegExp('^[A-Z]{1,2}\d[A-Z\d]?\s*\d[A-Z]{2}$') or literal /^[A-Z]{1,2}\d[A-Z\d]?\s*\d[A-Z]{2}$/i. Or click "Try in regex tester" to open it pre-loaded in Utilko's browser-based regex tester.Should I use this for security-critical validation?
Client-side regex is fine for UX (immediate feedback on a form). For anything security-critical — payments, auth, data integrity — always re-validate server-side using the same pattern PLUS domain-specific checks (Luhn checksum for cards, actual email delivery test, DNS resolution for domains).