Regex Tester & Visualizer

Test a regular expression against real text, see matches highlighted live, and get a plain-English breakdown of the pattern.

Pattern

/ /

Test string

Jordan Lee met Sarah Connor in New York last Tuesday.

Matches

Pattern breakdown

How this tool works

As you type a pattern, this tool compiles it using JavaScript's native RegExp engine — the exact same engine that runs in browsers and Node.js — so what you see here is exactly how the pattern will behave in real code, not an approximation. Matches against your test string are highlighted live, and the summary lists each individual match found.

The pattern breakdown works by walking through your regex character by character, recognizing common building blocks — character classes like \d or \w, anchors like ^ and $, quantifiers like * and +, and groups — and explaining each one in plain language. It's meant to help you read an unfamiliar pattern quickly, not replace a full regex reference for advanced constructs like lookaheads or named groups.

Frequently asked questions

What do the flags (like "g", "i", "m") actually do?
"g" (global) finds all matches instead of stopping at the first one; "i" makes matching case-insensitive; "m" (multiline) makes ^ and $ match the start/end of each line rather than the whole string. This tool automatically applies "g" so you always see every match.

Why does my regex work here but fail in [language X]?
Most regex syntax is broadly consistent across languages, but there are real differences — Python uses (?P<name>...) for named groups where JavaScript uses (?<name>...), for example. If something behaves differently elsewhere, check that specific language's regex documentation for syntax variations.

What's the difference between a capturing group and a non-capturing group?
A capturing group (...) saves what it matches so you can reference it later (like in a replacement string); a non-capturing group (?:...) groups part of the pattern for applying a quantifier or alternation without saving the matched text.

Is my test data sent anywhere?
No — matching happens entirely in your browser using JavaScript's built-in regex engine.

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