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Regex Tester & Debugger Online Free | MyToolbox

Test and debug regular expressions with live matching and highlighting. Free regex tester with flag support. No signup needed.

How to Use Regex Tester

  1. 1

    Enter your regex pattern

    Type your regular expression in the pattern field. Set flags like global (g), case-insensitive (i), or multiline (m) as needed.

  2. 2

    Paste your test string

    Enter the text you want to test against. The tool highlights all matches in real time.

  3. 3

    Review matches

    See all matches highlighted in the test string. Capture groups, match indices, and match count are displayed below.

Why Use Our Regex Tester

Live Match Highlighting

Matches are highlighted in real time as you type both the pattern and test string. No need to click "test" — results are instant.

Full Flag Support

Toggle global (g), case-insensitive (i), multiline (m), dotAll (s), and unicode (u) flags with checkboxes or inline flags.

Capture Group Display

Named and numbered capture groups are extracted and displayed for each match, making it easy to verify complex patterns.

Match Details

See the match count, individual match values, their positions in the input string, and the content of each capture group.

JavaScript Regex Engine

Uses the browser's native JavaScript regex engine, so behavior matches exactly what your JavaScript code will produce.

Frequently Asked Questions

Is the regex tester free?
Yes, completely free with no limits. Test as many patterns as you need without signup.
Is my test data private?
Yes. All regex evaluation happens in your browser using JavaScript's native regex engine. No data is sent anywhere.
What regex flavors are supported?
The tool uses JavaScript's regex engine (ECMAScript). This covers the vast majority of regex features including lookahead, lookbehind, named groups, and Unicode properties.
Can I use this to build regex for form validation?
Yes. A common workflow is to test your email, phone number, or URL validation patterns here, then copy the working regex into your code.
How does this compare to Regex101?
Regex101 offers more detailed explanations and supports multiple flavors (PCRE, Python, etc.). MyToolbox is faster for quick JavaScript regex testing with a simpler, distraction-free interface.
Does it support lookahead and lookbehind?
Yes. Both positive and negative lookahead (?= and ?!) and lookbehind (?<= and ?<!) are supported, as they are part of modern JavaScript regex.
Does this work on mobile?
Yes. The interface is responsive and works on any mobile browser, though a keyboard with easy access to special characters is helpful.
Can I test multiline patterns?
Yes. Enable the multiline (m) flag to make ^ and $ match the start and end of each line, or the dotAll (s) flag to make . match newlines.

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