What does it do?
It is a library of ready-made regular expressions for the validations every project needs: email, URL, Spanish DNI and NIE, IBAN, international and Spanish phone numbers, postal codes, strong passwords, dates, times, hex colours, IPv4 addresses, slugs, UUIDs and usernames.
Each pattern comes with:
- A description of what it accepts and its limits.
- Examples that should match and that should not, already tested.
- An explanation of every part of the regex.
- Copy for JavaScript/TypeScript, HTML, Zod, Angular and Python.
- Buttons to open it in the Tester or the Builder to adapt it.
Tip
Validate in the browser for a quick response to the user, and always validate again on the server: a client-side regex can be bypassed.
Frequently asked questions
›Is a regex enough to validate an email address?
No. A regex can reject obvious typos, but the only real check is sending a confirmation email. The RFC 5322 grammar is far too permissive and complex to be useful in a form.
›Do these patterns validate DNI letters or IBAN checksums?
No, they validate the format. The DNI control letter (number modulo 23) and the IBAN checksum (modulo 97) need a couple of lines of code after the regex.
›Can I use them in HTML forms?
Yes. Choose HTML in Copy for: you get an input with the pattern attribute, without the ^ and $ anchors that the browser adds by itself.