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Regex Tester

Our online Regex Tester (Regular Expression Tester) lets you test, analyze, and build JavaScript regular expressions live. Enter your regex pattern and see matches highlighted instantly on your test string. It features an interactive regex cheat sheet (click to insert), support for standard regex flags (global, ignore case, multiline, dotall), detailed pattern breakdown explanations, and capture group extraction. All processing runs 100% client-side in your browser to guarantee data privacy.

Cheat Sheet (Quick Insert)Click to insert token into pattern
Characters
Anchors & Boundaries
Quantifiers
Groups & Sets
//g
Flags:

Load Sample

Select a preset to populate pattern and test text:

How to use

  1. Select a sample preset or use the interactive Cheat Sheet to build your pattern.
  2. Type your regex pattern (without the surrounding slashes) and toggle flags (g, i, m, s) as needed.
  3. Paste or type your test string — matches will highlight instantly in the preview box.
  4. Scroll through the matches list below to inspect capture groups and character positions.

FAQ

Which regex flavor does this tool support?

This tester uses JavaScript's native RegExp engine. It is the exact same engine that runs in Google Chrome, Mozilla Firefox, Safari, and Node.js. A pattern that compiles and matches successfully here will run identically in your JavaScript app.

How does the interactive regex cheat sheet work?

The quick insert cheat sheet contains common regular expression wildcards (like digits, word boundaries, quantifiers, and groups). Simply click on any token badge, and it will be inserted directly at your current cursor position in the pattern input, making it easy to build expressions on the fly.

What do the regex flags (g, i, m, s) do?

g (global) finds all matches instead of stopping after the first match; i (case-insensitive) matches letters without distinguishing case; m (multiline) makes ^ and $ anchor to line starts and ends; s (dotall) allows the dot (.) character to match newline characters.

Is my text data safe and secure?

Yes, absolutely. Because this tool runs entirely client-side using JavaScript in your browser, your regular expression and test string never leave your device. We do not perform any server uploads, databases storage, or third-party transmissions of your input.

How are capturing groups and sub-matches extracted?

When your pattern contains capturing groups wrapped in parentheses (...), the tool extracts their captured text for each match. They are displayed under each match block as Group #1, Group #2, etc. If a group is optional and was not captured, it will be marked as 'no match'.