Regex Tester

How it works

1. Enter your regular expression in the Pattern field, without the surrounding slashes. For example \b\w+@\w+\.\w+\b to find email-like strings.
2. Set the flags you need: g for all matches, i for case-insensitive, m for multi-line anchors, s so that a dot matches newlines, u for full Unicode support.
3. Paste the text you want to search into the input box. Log lines, CSV rows, HTML, whatever your pattern is meant to run against.
4. Press Test regex. The output lists each match with its position and every numbered or named capture group, so you can confirm the pattern grabs exactly what you expect.

Frequently asked questions

Which regex flavor does this tester use?

It uses the JavaScript (ECMAScript) engine built into your browser. Lookbehind, named groups (?<name>...), Unicode property escapes \p{...} with the u flag, and the s flag are all supported in current browsers. Features specific to PCRE, Python or Java, such as possessive quantifiers or inline modifiers like (?i), are not available.

Why do I only see the first match?

Without the g flag, a regular expression stops after the first match. Add g to the Flags field to list every occurrence in the text.

What do the flags mean?

g: global, find all matches. i: ignore case. m: ^ and $ match at the start and end of each line rather than the whole text. s: the dot also matches line breaks. u: treat the pattern and text as Unicode code points, needed for emoji and \p{L} classes. y: sticky, match only at the current position.

Is my sample text uploaded anywhere?

No. Matching runs entirely in the browser. You can safely paste production logs, personal data or source code; the text never leaves your device.

Why does my pattern hang or take a long time?

Some patterns, especially nested quantifiers like (a+)+ on non-matching input, cause catastrophic backtracking. Make quantifiers more specific, use atomic-style alternatives such as possessive character classes, or anchor the pattern to reduce the search space.