Email addresses
pattern = \b[a-z]+@[a-z]+\.[a-z]{2,}\bflags = gitext = Contact alice@example.com or bob@example.org.
Result: 2 matches: alice@example.com (index 8) · bob@example.org (index 31)
Regex Tester
Write a regular expression, choose flags, and see every match highlighted with its position and capture groups — instantly, as you type. Invalid patterns get a clear error instead of a crash, and runaway matches are capped to keep the page responsive. Everything runs in your browser.
Privacy: this tool processes your data entirely in your browser. Nothing you paste or type is sent to the server.
Enter your values and press Calculate — the result appears here.
Worked examples
Capture groups
pattern = (\d{4})-(\d{2})-(\d{2})flags =text = Date: 2023-11-14
Result: 1 match: 2023-11-14 with groups [2023, 11, 14]
Invalid pattern
pattern = (unclosedflags =text = x
Result: Invalid pattern: missing closing parenthesis
Frequently asked questions
Which regex flavor is used?
JavaScript (ECMAScript) regular expressions — the same engine as your browser. If you are porting from PCRE or Python, some syntax such as lookbehind may behave slightly differently.
Why does the match count stay small on huge inputs?
To keep the page responsive, the tester reports the first 500 matches and notes when it stopped. The pattern itself is still evaluated by the browser.
Are my patterns and text sent anywhere?
No. Everything runs locally in your browser — safe for testing patterns against confidential log lines or personal data.
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