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Clear instructions
Find steps, examples and limitations below.
Use online
Open the tool in a supported web browser.
Free to use
No sign-up required. Tool-specific limits may apply.
Reference resources
- Regex Cheat Sheet
JavaScript regex tokens, flags and tested-pattern examples.
How to use the Regex Tester
Test JavaScript regular expressions against sample text and inspect matches.
- 1 Enter the expression between the displayed slash delimiters.
- 2 Choose flags such as global, ignore case or multiline and paste Test string.
- 3 Review Highlighted matches, match totals and Match details.
Example and practical tips
Try a short digit-matching pattern on text containing two numbers, then toggle the global flag.
Frequently asked questions
Will this match another regex engine exactly?
Not necessarily. Syntax and Unicode handling vary by language; this tool uses the browser’s JavaScript engine.
Can a pattern freeze the browser?
Very complex or backtracking-heavy patterns can be slow. Test a small sample before increasing input size.
Practical guides
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How to Use Regex Tester
Test JavaScript regular expressions online with live match highlighting and flags. See every match in your sample text. Free regex tester for developers.
Report an issue
Something broken or not quite right? Tell us and we will look into it.