Regex Tester

What is the Regex Tester?

Test a regular expression against text and list every match with its position. Testing a regular expression against real text shows every match and its position, so you can fix patterns before they go into code.

How to use the Regex Tester

1. Paste or type your your text into the box (a sample is pre-filled so you can see how it works).
2. Results update automatically as you type; you can also press Calculate.
3. Read the output: result.
4. Use the 📊 chart to see the result visually, then copy or share it.

Where the Regex Tester helps in real life

A developer writes a pattern to find US phone numbers in support tickets. Testing it on sample text shows which formats it catches and which it misses.

A data analyst needs to pull dates out of messy notes. Trying the pattern here first avoids a script that silently skips half the rows.

Common mistakes to avoid

• Forgetting to escape dots and brackets that should match literally.
• Using a greedy .* that swallows far more text than intended.
• Testing only the happy path and not edge cases.
• Copying a pattern written for a different regex flavor.

💡 Practical tip: Greedy patterns like .* can match much more text than expected.

Tips for better results

• Test with many examples.
• Use anchors when needed.
• Check performance on long text.

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