Breezy Tools

Regex Tester

Test regular expressions against sample text with real-time match highlighting.

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How to Use Regex Tester

  1. 1

    Enter your regex pattern

    Type or paste a regular expression into the pattern field. The tool uses JavaScript's RegExp engine.

  2. 2

    Set regex flags

    Toggle common flags like global (g), case-insensitive (i), and multiline (m) to control matching behavior.

  3. 3

    Add test text

    Enter the text you want to match against. Matches are highlighted in real time as you type.

  4. 4

    Review matches and groups

    View all matches and their captured groups displayed below the test text. Use this to verify your pattern works as expected.

Key Features

Real-Time Highlighting

Matches are highlighted instantly in the test text as you type or modify your regex pattern.

Capture Group Display

Each match shows its captured groups so you can verify that subpatterns extract the correct data.

Common Flag Support

Toggle global, case-insensitive, multiline, and other flags with a single click.

Match Counter

See the total number of matches at a glance, making it easy to confirm your pattern's coverage.

Common Use Cases

  • Form Validation Patterns

    Build and test regex patterns for validating email addresses, phone numbers, postal codes, and other user inputs.

  • Log File Parsing

    Create patterns to extract timestamps, error codes, or IP addresses from server logs before writing a parsing script.

  • Search and Replace

    Prototype find-and-replace patterns for code editors or build scripts to ensure accuracy before applying them to production files.

Frequently Asked Questions

Which regex engine does this tool use?▾

It uses your browser's native JavaScript RegExp engine, which follows the ECMAScript specification. Patterns compatible with JavaScript will work here.

Does this tool support lookbehind assertions?▾

Yes, if your browser supports them. Most modern browsers (Chrome, Edge, Firefox, Safari 16.4+) support both lookahead and lookbehind assertions.

Can I test regex for other languages like Python or Java?▾

The tool uses JavaScript regex syntax. While many patterns are compatible across languages, features like named groups or possessive quantifiers may differ. Always verify in your target language.

Is my test data stored anywhere?▾

No. All processing happens locally in your browser. Your regex patterns and test text are never sent to any server.