Regex tester & explainer
Type a pattern, pick flags, paste a test string, and see matches highlighted instantly — plus a plain-English walkthrough of what each piece of the regex does.
Common patterns
Pattern
Flags
Active flags:
Test string
Validity
Enter a pattern to test it against the string above.
Valid pattern with flags .
Invalid pattern —
Highlighted matches
Match list
| # | Match | Index | Groups |
|---|---|---|---|
— |
Pattern breakdown
Plain-English notes for common constructs. This is a helper, not a full regex parser — complex or nested patterns may get approximate rows.
| Token | Meaning |
|---|---|
Everything runs in your browser — your pattern and test string never leave this page. Matching uses the JavaScript RegExp engine, which differs from PCRE in a few edge cases (lookbehind limits, Unicode properties, etc.).
About this tool
A regex tester lets you iterate on a regular expression against sample text before you ship it in code, a search-and-replace, or a validation rule. This one highlights every match, lists capture groups, and explains each token in plain English so you can sanity-check what you wrote.
Under the hood it uses the same RegExp constructor your browser and Node.js use — not PCRE. That means features like named groups and lookbehind work in modern engines, but syntax and edge cases can differ from Perl, Python, or grep.
Flags— g finds all matches; i ignores case;m makes ^ and$ match line boundaries; s lets. span newlines; u enables full Unicode mode; y sticky matching starts only atlastIndex.