Regex Tester

Regex Tester guide

The Regex Tester lets you test JavaScript regular expressions against sample text and see matches before using the pattern in code. It is a safer way to build patterns for validation, extraction, search-and-replace planning or log inspection.

Regular expressions can be powerful but easy to misread. Testing with realistic examples and edge cases helps avoid patterns that work only for the first happy-path string.

When to use it

• Testing an email, slug, ID or filename validation pattern.
• Extracting IDs, dates or codes from logs and pasted text.
• Checking capture groups before using a pattern in JavaScript.
• Debugging why a pattern is too greedy or not matching Unicode text.

How to use it

1. Enter the regular expression pattern and flags supported by JavaScript.
2. Paste realistic sample text with both matching and non-matching examples.
3. Review highlighted matches and capture groups.
4. Adjust anchors, character classes and quantifiers until the result is correct.
5. Test edge cases before copying the pattern into production code.

Example

Pattern: \b[A-Z]{2}-\d{4}\b, Text: Ticket DK-2026 is ready.

Match: DK-2026

Privacy

Patterns and test text stay in your browser. UtilityTools.eu does not receive the text you use for testing.

Limitations and accuracy notes

• The tool uses JavaScript regular expression behavior, which can differ from PCRE, Python, Java or .NET.
• A regex that works on examples can still fail on real-world messy data.
• Complex patterns can be hard to maintain and may perform poorly on very long input.

FAQ