Utilities Web
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Regex Tester

Real-time regex testing and matching

How to Use

  1. Enter a regular expression pattern in the pattern input field
  2. Enter a test string in the input field
  3. Match results are highlighted in real time
  4. Switch flags (g, i, m, s, u) as needed
  5. When replacement mode is enabled, you can also see the conversion result using the replacement pattern

Use Cases

  • When prototyping and validating validation patterns for form input
  • When creating regular expressions to extract specific patterns from log files
  • When pre-checking bulk replacement patterns for text
  • When visually checking the behavior of capture groups in regular expressions

Frequently Asked Questions

Which regular expression engine (flavor) is supported? ▼

We use the JavaScript regular expression engine. It complies with the ECMAScript specification and supports the latest features such as named capture groups and Unicode property escapes.

How do I distinguish between flags (g, i, m, etc.)? ▼

g (global) searches for all matches, i (ignore case) does not distinguish between uppercase and lowercase. m (multiline) matches ^ and $ at the beginning and end of each line, s (dotAll) matches . to newlines as well.

Are there performance issues with complex regular expressions? ▼

Patterns such as extremely nested quantifiers (e.g., (a+)+) may cause the browser to become unresponsive temporarily, but normal regular expressions are not a problem.

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