Free Regex Tester – Test Regular Expressions Online

It supports all the standard JavaScript flags: g (global, finds all matches), i (case-insensitive), m (multiline, so ^ and $ match line starts and ends), s (dotAll, so the dot matches newline characters), and u (unicode, for correct handling of characters beyond the basic set). You can combine flags freely, for example using g and i together to match all occurrences regardless of case.

Helperzy Regex Tester mein apna pattern aur test string daalo. Matches automatically highlight ho jayenge — bilkul free. Capture groups bhi alag se dikhte hain, jisse aap confirm kar sakte ho ki pattern sahi part capture kar raha hai. Sab kuch browser mein chalta hai.

Yes. All capture groups, including numbered groups and named groups, are shown in the match details panel below the test string. Each match lists what every group captured, so you can verify that your parentheses isolate the right portions of the text before you use them in code. This is especially helpful when extracting structured data like dates or URLs.

Mostly, but not entirely. Helperzy uses the JavaScript regex engine since it runs in your browser. Many patterns work identically in Python, but some syntax differs — Python uses (?P<name>...) for named groups while JavaScript uses (?<name>...), and lookbehind and certain escapes behave differently. Use the results as a strong guide, then confirm engine-specific features when targeting Python.

Common causes include forgetting the g flag when you expect multiple matches, special characters like ., +, *, (, or ? not being escaped with a backslash when you mean them literally, or case sensitivity blocking a match when you needed the i flag. Paste your pattern here and watch the live highlighting — it usually makes the problem obvious within a few edits.

The g flag tells the engine to find every match in the string instead of stopping at the first. The i flag makes matching ignore upper and lower case, so 'Cat' matches 'cat'. The m flag changes ^ and $ to match the beginning and end of each line rather than the whole string, which matters when your test text spans multiple lines.

Yes. Once your pattern matches the right text, you can use the same regular expression in your editor or code's find-and-replace function with capture group references like $1 or \1 to restructure text. Testing the match here first means you can be confident the replacement will target exactly the parts you intend before running it on real files.

Yes. All matching happens entirely in your browser using JavaScript — nothing you type is uploaded to a server or stored. That makes it safe to test patterns against logs, sample records, or other private text. As always, avoid pasting real production secrets anywhere you do not need to, but the tool itself never transmits your data.

For emails a practical pattern is something like [\w.+-]+@[\w-]+\.[\w.-]+, which matches a local part, an @ sign, and a domain. Phone numbers vary by country, so build the pattern around the format you expect. Paste real examples into the test string and refine the pattern until every valid case highlights and invalid ones do not.

By default quantifiers like * and + are greedy, meaning they match as much text as possible. Adding a ? makes them lazy, matching as little as possible. For example, with the text <a><b>, the pattern <.*> matches the whole thing greedily, while <.*?> matches just <a>. Testing both here side by side makes the difference clear instantly.