Regex Tester: Learn and Test Regular Expressions Online

Regular expressions (regex) are powerful but tricky. Use our online regex tester to experiment with patterns and see matches in real-time.

What are Regular Expressions?

Regex patterns let you search for text patterns, validate input, find and replace text, and extract data from strings.

How to Use the Regex Tester

1. Enter your pattern (e.g.,

   [a-z]+

   )
2. Add flags if needed (g, i, m)
3. Enter test text
4. See matches instantly

Common Regex Patterns

Email Validation

[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}

Phone Numbers

\d{3}[-.]?\d{3}[-.]?\d{4}

Extract JSON Keys

Use regex to find patterns in JSON data:

"([^"]+)":\s*

Find JWT Tokens in Logs

Extract JWT tokens from server logs:

eyJ[A-Za-z0-9_-]+\.eyJ[A-Za-z0-9_-]+\.[A-Za-z0-9_-]+

Find Base64 Strings

Identify Base64 encoded content:

[A-Za-z0-9+/]{20,}={0,2}

Regex Flags

• g (Global) - Find all matches
• i (Insensitive) - Case-insensitive
• m (Multiline) - ^ and $ match line starts/ends

Complete Your Dev Toolkit

• JSON Formatter - Format and validate JSON
• Base64 Encoder - Encode/decode strings
• JWT Decoder - Debug auth tokens

Conclusion

Testing regex patterns is essential before using them in code. Our free regex tester shows matches in real-time.