Regex Tester

DEV

Test regular expressions live with match highlighting. Supports all JavaScript regex flags.

Regular Expression

Test String

📖 How to Use Regex Tester

Enter your regex pattern

Type your regular expression in the pattern field (without forward-slash delimiters).

Set flags

Toggle flags: g (global — find all matches), i (case-insensitive), m (multi-line), s (dotAll).

Enter test string

Type or paste the text you want to match against.

See matches highlighted

All matches are highlighted in the test string, with match groups listed below.

💡 Examples

Email extraction

INPUT

Pattern: \b[A-Z0-9._%+-]+@[A-Z0-9.-]+\.[A-Z]{2,}\b (flag: i)

→

OUTPUT

Matches all valid email addresses in the text

Date validation

INPUT

Pattern: ^\d{4}-\d{2}-\d{2}$

→

OUTPUT

Matches dates in YYYY-MM-DD format

URL matching

INPUT

Pattern: https?://[^\s]+

→

OUTPUT

Matches http:// and https:// URLs

🚀 Pro Tips

✓Use `\b` word boundaries to match whole words only and avoid partial matches.

✓`.+` matches one or more of any character (except newline). Use `.*` for zero or more.

✓Use non-capturing groups `(?:...)` when you group without wanting capture group references.

✓Test with edge cases: empty string, very long string, Unicode characters, and newlines.

✓The `?` after a quantifier makes it non-greedy: `.*?` matches as few characters as possible.

❓ Frequently Asked Questions

What regex flavour does this tester use?+

It uses JavaScript's built-in RegExp engine, which is ECMAScript-compliant and supports most standard regex features.

How do I match a literal dot or bracket?+

Escape special characters with a backslash: \. matches a literal dot, \[ matches a literal bracket.

What is the difference between greedy and lazy matching?+

Greedy quantifiers (.*) match as much as possible. Lazy quantifiers (.*?) match as little as possible. Lazy is often better for extracting content between tags.

Can I use this to validate emails or phone numbers?+

Yes — regex is commonly used for format validation. However, for production apps, use well-tested library functions since edge cases in email/phone formats are tricky.

More Developer Tools Tools

JSON Formatter Base64 Encoder/Decoder URL Encoder/Decoder Hash Generator UUID Generator JWT Decoder CSS Minifier HTML Entities Encoder