Regex Tester

About the Regex Tester

Test regular expressions online with live match highlighting. Enter a pattern, paste sample text, and see matches, groups, and positions update as you type - a free, private regex debugger that runs entirely in your browser.

Regular expressions are powerful and notoriously tricky — an unescaped dot, greedy quantifier, or wrong anchor silently changes what your pattern matches. Testing against real input strings before deploying is the only reliable way to confirm a pattern does what you think.

This tester shows matches in real time as you type, with capture groups, match indices, and flag controls (global, case-insensitive, multiline). Pattern and input stay in your browser, safe for testing against production log samples or user data.

Use cases and examples

Build a validation pattern iteratively: try emails, phone numbers, or slugs against realistic samples until it matches exactly what you intend.

Understand a regex you found in code: paste it with sample input and watch which alternatives and groups fire.

Prepare a safe pattern for splitting or replacing text, verifying greedy versus lazy behavior before it hits production.

Pattern: /^(\+\d{1,3})?[\s-]?(\d{3})[\s-]?(\d{3})[\s-]?(\d{4})$/
Matches: +1 555-123-4567, 5551234567

How to use

1. Enter your regular expression in the pattern field.
2. Choose the flags you need (g, i, m) or write them inline.
3. Type or paste test strings — matches highlight as you type.
4. Inspect capture groups to verify what each part of your pattern captures.

Frequently Asked Questions