Regex Tester & Debugger

Test, highlight, and debug your Regular Expressions instantly in your browser.

Regular Expression
/
/
Invalid Regular Expression
g (Global)
i (Case Insensitive)
m (Multiline)
s (Dotall)
u (Unicode)
Test String
Live Match Result 0 Matches
Substitution
Replaced Result
Match & Capture Group Breakdown
Match # Full Match Capture Groups Index
Waiting for valid regex and test string...

What we do

Live Syntax Highlighting

Watch your matches light up instantly as you type. Our real-time engine applies accurate highlighting to your test text without requiring you to click a submit button.

Capture Group Mapping

Working with complex data extraction? Our intelligent breakdown table beautifully maps numbered and Named Capture Groups directly to their extracted values.

Real-Time Substitution

Format text instantly. Use `$1`, `$2`, or `$` in the substitution box to seamlessly inject captured regex groups into your new replacement string.

Visual Flag Toggles

Easily experiment with regex behavior by toggling Global (g), Case-Insensitive (i), Multiline (m), and Dotall (s) flags using our intuitive quick-toggle buttons.

Catastrophic Safeguards

Our intelligent background Web Worker architecture prevents infinite loops. If a complex regex triggers Catastrophic Backtracking, the engine safely intercepts it without freezing your browser.

100% Client-Side Privacy

Testing regex against proprietary database dumps or sensitive user data? Your text never leaves your computer. Everything is executed locally in your browser.