Strong Password Regex

Validation

Regular expression

/^(?=.*[a-z])(?=.*[A-Z])(?=.*\d)(?=.*[^A-Za-z0-9]).{12,}$/

Pattern breakdown

Part	Meaning
`Anchor or context`	Use anchors when you need whole-string validation.
`Main token`	The core token sequence describes the accepted text shape.
`Character class`	Character classes limit which characters are valid.
`Quantifier`	Quantifiers control how many characters or groups are accepted.
`Flags`	Use language-specific flags such as i, m, or u only when needed.

Should match

Toolumina!2026
Toolumina!2025

Should not match

password
not matching sample
Toolumina!2026 invalid
passwordToolumina!2026

Test cases

Input	Expected	Why it matters
`Toolumina!2026`	Match	Representative valid input for this pattern.
`Toolumina!2025`	Match	Representative valid input for this pattern.
`password`	No match	Common invalid or boundary input.
`(empty string)`	No match	Common invalid or boundary input.
`not matching sample`	No match	Common invalid or boundary input.
`Toolumina!2026 invalid`	No match	Common invalid or boundary input.
`passwordToolumina!2026`	No match	Common invalid or boundary input.

JavaScript

const re = /^(?=.*[a-z])(?=.*[A-Z])(?=.*\d)(?=.*[^A-Za-z0-9]).{12,}$/;
re.test(input);

Python

import re
bool(re.search(r"^(?=.*[a-z])(?=.*[A-Z])(?=.*\d)(?=.*[^A-Za-z0-9]).{12,}$", text))

PHP

$ok = preg_match('/^(?=.*[a-z])(?=.*[A-Z])(?=.*\d)(?=.*[^A-Za-z0-9]).{12,}$/', $value) === 1;

Java

Pattern pattern = Pattern.compile("^(?=.*[a-z])(?=.*[A-Z])(?=.*\\d)(?=.*[^A-Za-z0-9]).{12,}$");
pattern.matcher(value).find();

Go

re := regexp.MustCompile(`^(?=.*[a-z])(?=.*[A-Z])(?=.*\d)(?=.*[^A-Za-z0-9]).{12,}$`)
ok := re.MatchString(value)

Notes and production use

Strong Password regex is useful as a practical starting point. Test it against your real input, avoid using it as the only security control, and prefer a parser when the format has complex grammar.

Performance tip: avoid running complex regular expressions repeatedly on very large untrusted strings without limits. Prefer anchored validation patterns, cap input length before matching, and use a parser when the target format has nested grammar.

Strong Password