Regex Pattern Library

They are solid starting points that cover the most common valid inputs, but no single regex perfectly handles every edge case for every locale or standard. Email validation is a classic example: the full RFC 5321 pattern is enormous, while a simple one misses many valid addresses. Use these patterns as a verified foundation, then test them against your specific data and adjust as needed before shipping.

Global (g) finds all matches in the text instead of stopping after the first one. Case Insensitive (i) treats uppercase and lowercase as equivalent — "Email" and "email" both match /email/i. Multiline (m) changes how ^ and $ behave: without it they match the start and end of the whole string; with it they match the start and end of each line. Most validation patterns use global off (you just need to know if it matches at all), but for log parsing or extraction global is usually what you want.

Yes. The Regex Pattern input in the test panel is fully editable. Type any pattern, set the flags you need, paste your test text, and see matches highlighted immediately. The panel does not require you to select a pattern from the library — it works as a standalone regex tester. Click Clear to reset both the pattern and the test text.

The test panel uses JavaScript's built-in RegExp engine (ECMAScript regex), which is the same engine running in Node.js, Chrome, Firefox, Safari, and Edge. Most patterns in the library are compatible with Python (re module), PHP (PCRE), Java, and other flavors — but there are differences: JavaScript does not support lookbehind in older engines, named groups use (?<name>) syntax, and possessive quantifiers are not supported. Test edge cases in your target environment before deploying.

First, toggle the Global flag to see if there are multiple matches you did not expect. Then check anchors: without ^ at the start and $ at the end, the pattern can match a substring anywhere in the text (so /\d+/ matches "abc123def"). Anchoring to the full string with /^\d+$/ forces an exact match. If too little matches, check for special characters that need escaping — in regex, . * + ? ( ) [ ] { } ^ $ | \ all have special meaning and must be escaped with \ to be treated as literals.

Use the search bar at the top of the library and type a keyword like "credit card", "hex color", "mac address", or "postal code". The search matches pattern names, descriptions, and the regex text itself. If you still do not find what you need, copy the closest existing pattern into the test panel and modify it — for example, adapt the IPv4 pattern to match a specific subnet, or adjust the date pattern for your locale's date format.

No. All regex matching happens entirely in your browser using JavaScript. Your text, patterns, and results never leave your machine. There is no server involved at any point, so you can safely test against log files, emails, passwords, or any sensitive data.