Regex Tester – Free Online Regular Expression Sandbox

Build, test, and debug your regular expressions with this interactive sandbox. Enter your pattern and test string to see live matches highlighted instantly. Supports all standard JavaScript RegEx flags (Global, Case-insensitive, Multiline, DotAll, Unicode, Sticky) and provides detailed information about capture groups for each match. Perfect for developers, data scientists, and anyone learning or working with patterns. Runs 100% in your browser — your data is never sent to any server.

//gi
73 chars
Highlighter Preview2 matches
Hello! My email is test@example.com and backup is dev.user@company.co.uk.
Matches & Groups
Match 1index: 19
test@example.com
Match 2index: 50
dev.user@company.co.uk

★How to Use the Regex Tester

Build Your Pattern:

  1. Enter your Regular Expression in the pattern field (e.g. [a-z]+).
  2. Toggle Flags like ignore case (i) or global (g) using the checkboxes.
  3. Paste your Test String in the large text area below.
  4. Matches will be highlighted in real-time as you type.

Inspect Results:

  • Highlights: Different matches are highlighted to help you visualize boundaries.
  • Capture Groups: See which parts of your regex captured which text segments.
  • Stats: View the total number of matches and error messages if your regex is invalid.