Regex Tester
Test JavaScript regular expressions against sample text, inspect matches and capture groups, set flags, and preview replacements directly in your browser.
What this tool solves
Test a regular expression against sample text and inspect matches for pattern, group and rule debugging.
Input: a JavaScript-style regular expression, optional flags and sample text.
Output: match positions, captured groups and replacement preview.
How to use it
- Enter the pattern without surrounding prose and choose flags such as g, i or m only when needed.
- Paste representative sample text, including edge cases that should match and should not match.
- Inspect captures and replacement output; test several inputs before using a pattern in production code.
Common use cases
- Debug validation and parsing patterns
- Prototype find/replace expressions
- Learn how groups, anchors and flags affect matches
Privacy, accuracy and limits
The tester follows JavaScript RegExp behavior. Other regex engines such as PCRE, .NET, Java or Python can support different syntax and semantics.
WebToolMint keeps this workflow local in the browser where the feature allows it. Network-dependent tools are labelled separately. Keep originals and independently verify results that affect legal, financial, medical or business decisions.
Frequently asked questions
Why does a regex work in one language but not here?
Regular-expression engines differ. This tester targets JavaScript RegExp syntax and behavior.
What does the g flag do?
It searches for multiple matches instead of stopping after the first match.
Can a regex validate every email address perfectly?
A simple regex can catch common formatting issues, but full email-address rules and deliverability are more complex than a short pattern.