JavaScript Regex Tester
Regular expressions
Regex Tester
Test JavaScript regular expressions against sample text and inspect matches.
Tool tool
Usage guide
Test JavaScript regular expressions against realistic sample text
Regular expressions can fail because of escaping, flags, greediness, character classes, or assumptions about line boundaries. Testing representative input before shipping a pattern helps uncover matches you intended, matches you missed, and text you captured accidentally.
How to use Regex Tester
- 1.Enter the pattern without surrounding slashes unless the field specifically expects them, then choose the needed flags.
- 2.Paste several realistic examples including cases that should match and cases that should not.
- 3.Inspect every match and captured group, then tighten the expression before moving it into production code.
Examples
- Test an email-like pattern against valid examples, malformed values, and surrounding punctuation.
- Use the multiline flag when anchors should apply to individual lines rather than only the whole string.
- Compare greedy .* with a narrower expression when matching repeated delimiters.
Limitations and notes
- A regex match does not prove that complex data such as an email address, URL, or date is semantically valid.
- Poorly designed expressions can be slow on large or adversarial input, so performance-sensitive code needs separate testing.
Why does my regex work in one language but not another?
Regex engines differ in syntax, flags, Unicode behavior, and supported features. This tester follows JavaScript regular-expression behavior.
What does the g flag do?
The global flag finds successive matches instead of stopping after the first match, which is useful when scanning an entire text.
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How the regex tester works
Paste or enter the code, data, or value you want to inspect.
The tool processes it locally in your browser.
Copy the formatted output or converted value for your project.
Frequently Asked Questions
Is the regex tester free?
Yes. It is free and does not require an account.
Is my code sent to a server?
No. These developer tools run locally in your browser.
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