Regex Tester
Test and debug regular expressions in real-time. Support for flags, match highlighting, and common regex patterns. Free online regex tester.
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regexTester.replace
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What is Regex Tester?
Regular expressions (regex) are powerful pattern-matching tools for text processing, but they can be notoriously difficult to write and debug. Our Regex Tester provides an interactive environment to test, validate, and optimize your regular expressions against real text in real-time.
Whether you're validating email addresses, extracting data from log files, parsing complex text formats, or building search-and-replace patterns, this tool helps you get your regex right before deploying it to production. See matches highlighted instantly, get detailed explanations of your patterns, and identify errors before they cause problems.
The tester runs entirely in your browser with no server-side processing. Your test data and patterns are private and never transmitted. Support for JavaScript regex syntax with PCRE compatibility ensures patterns work across different programming environments.
How to use
- 1 Enter your regular expression pattern in the regex input field
- 2 Select the appropriate flags (g, i, m, s, u, y) for your use case
- 3 Type or paste your test text in the text area below
- 4 Watch matches highlight in real-time as you type
- 5 Click on individual matches to see capture group details
- 6 Use the replace tab to test replacement patterns
- 7 Copy the final regex code in your preferred programming language
Common use cases
- ✓ Validating user input: email addresses, phone numbers, zip codes
- ✓ Extracting data from logs: IP addresses, timestamps, request IDs
- ✓ Text processing and transformation: find and replace operations
View full documentation for more use cases →