Regex Generator

Use the Pattern Library tab to pick from 20+ common patterns, or switch to the Custom Builder tab to construct your own regex piece by piece using character classes, quantifiers, groups, and modifiers. Everything updates live as you build.

Yes. Type or paste any text in the Test String area and matches are highlighted in real-time. Match groups and their positions are shown below the highlighted output.

Regex syntax varies between programming languages. The Escaped Output tab shows your regex properly formatted as a string literal for JavaScript, Python, Java, and PHP so you can paste it directly into your code.

A capturing group (...) saves the matched text for back-references and extraction. A non-capturing group (?:...) groups content for quantifiers but doesn't create a capture, improving performance when you don't need the matched text.

No. Everything runs 100% in your browser. No text, patterns, or data are sent to any server.

A practical pattern is ^[\w.+-]+@[\w-]+\.[\w.-]+$ — it accepts the common local-part characters, requires an @, and checks the domain has at least one dot. Full RFC 5322 compliance is far more complex and rarely needed; for most apps this pattern plus a confirmation email is the right balance. Use the pattern builder above to assemble it and test it against sample addresses.

Flags modify how the whole pattern matches: g (global) finds all matches instead of stopping at the first, i (ignore case) makes the match case-insensitive, m (multiline) makes ^ and $ match at line boundaries, and s (dotall) lets . match newlines. Combining them, e.g. /pattern/gi, is common when processing whole documents.

For the ISO format YYYY-MM-DD use ^\d{4}-\d{2}-\d{2}$. To also reject impossible months or days, use ^\d{4}-(0[1-9]|1[0-2])-(0[1-9]|[12]\d|3[01])$, which restricts the month to 01-12 and the day to 01-31. True calendar validation (leap years, 30-day months) is best left to a date library after the regex pre-filter.