Regex Tester
Test a regular expression against a string in the browser. Example:
^[A-Z]{2}[0-9]{4}$ with AB1234.
Invalid or huge patterns are rejected. Matching is capped so a bad regex cannot freeze the tab for long.
Flags (how the pattern is applied)
| # | Match | Index | Groups |
|---|---|---|---|
| Run Test to see matches. | |||
About Regex Tester
Test and debug regular expressions online with this free regex tester. Enter a pattern with flags, paste sample text, and see matches, capture groups, and match counts highlighted in real time so you can refine the expression before using it in code. It helps with validation rules, log parsing, search and replace tasks, and extracting ids from messy text.
Regular expressions are powerful and easy to get slightly wrong. A tester that shows groups saves you from shipping a pattern that matches the whole line when you only wanted a capture. Frontend developers test email and phone patterns. Backend developers test log lines and routers. Data people extract fields from exports. Flags such as case-insensitive and multiline change results; seeing that live is faster than redeploying.
Paste representative samples, including cases that should not match. Count of matches tells you whether you accidentally matched too much. Copy the final pattern into JavaScript, a language with similar syntax, or a config file. Remember that flavors differ; this tester uses the browser engine, which is close to JavaScript regex. Python, Java, and POSIX may still need a final check in those runtimes.
Everything is evaluated in your browser, so patterns and test data stay private. Customer logs and PII in samples are not uploaded. Use this free online regex tester and regular expression debugger whenever you need live matches and capture groups with privacy.