Regex Tester
Write a regular expression, paste sample text, and see the matches highlighted in real time. It is built for the trial-and-error that regex always involves - you adjust the pattern and immediately see what it catches and what it misses.
Regex Tester & Pattern Matcher
Enter a regular expression, toggle flags, provide sample text, and instantly see all matches.
Why a live tester saves hours
Regular expressions are powerful but unforgiving: a pattern that looks right often matches too much or too little, and you cannot tell until you run it on real data. A live tester closes that loop. You see every match as you type, so you can tighten or loosen the pattern against actual examples instead of guessing and re-running code.
It is especially useful for the cases that break naive patterns - optional parts, escaped special characters, and greedy versus lazy matching that quietly grabs more than intended.
Building a pattern that holds up
Test against the messy reality, not just the clean example.
- Include edge cases in your sample text: empty values, extra spaces, and near-misses you do NOT want to match.
- Anchor with ^ and $ when a value must match in full, not just somewhere inside.
- Prefer specific character classes over '.' so the pattern does not silently match things it should not.
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FAQs
Which regex flavor does this use?▼
It uses JavaScript's regular expression engine, the same one in browsers and Node.js. Most syntax is shared across languages, but features like lookbehind or named groups can differ from Python, PCRE, or Java, so test in your target environment for anything advanced.
What do the flags (g, i, m) mean?▼
g (global) finds all matches instead of stopping at the first; i (insensitive) ignores letter case; m (multiline) makes ^ and $ match at each line break. You combine them as needed for the behavior you want.
Why does my pattern match more than expected?▼
Usually because quantifiers are greedy by default - .* grabs as much as possible. Make it lazy with .*? or use a more specific character class so it stops where you intend.
How do I match a literal special character like a dot or bracket?▼
Escape it with a backslash. A bare '.' matches any character, but '\.' matches an actual period. The same applies to ( ) [ ] { } + * ? and others.
Is my test text sent to a server?▼
No. Matching runs in your browser, so both the pattern and the sample text stay on your device.
What is the difference between greedy and lazy matching?▼
Greedy quantifiers (* + {n,}) match as much as possible, then back off if needed. Lazy versions (*? +?) match as little as possible. Lazy is what you want when extracting the shortest run between two markers.
How do capturing groups work?▼
Parentheses create a group you can extract or reuse. ( ) captures, while (?: ) groups without capturing. Captured groups are how you pull out parts of a match, like the area code from a phone number.
Why is my regex slow or freezing the page?▼
Certain patterns cause 'catastrophic backtracking', where nested quantifiers explode in cost on some inputs. Simplify nested groups and avoid patterns like (a+)+ to keep matching fast.
How do I match across multiple lines?▼
Use the m flag so ^ and $ work per line. To let '.' match newlines as well, use the s (dotAll) flag, since by default '.' does not match a line break.
Can I use this to validate an email or URL?▼
You can draft a pattern, but fully validating emails or URLs with regex is notoriously hard and error-prone. For those, a basic sanity-check pattern plus real verification (like sending a confirmation) is more reliable than a perfect regex.
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