Free Online Regex Tester
Validate regular expression syntax with immediate feedback. Inspect full matches, capture groups, and indices in a safe, client-side sandbox.
Three simple steps to process your files
Enter Regular Expression
Type or paste your pattern in the regex field, selecting any desired matching flags.
Input Test Text
Paste the string or log excerpt you want to validate against your pattern.
Inspect Matches & Groups
View highlighted matching substrings, total match counts, and capture group breakdowns in real time.
Engineered for speed, fidelity & security
Full Flag Configuration
Toggle global (g), case-insensitive (i), multiline (m), dotAll (s), unicode (u), and sticky (y) flags.
Real-Time Match Highlighting
Visual color-coded highlight overlay on your test string updating as you type.
Capture Group Explorer
Detailed breakdown of full matches and numbered or named capture groups with character positions.
Instant Syntax Error Diagnostics
Immediate feedback on unescaped parentheses, invalid range quantifiers, and syntax mistakes.
One-Click Pattern Presets
Built-in regex templates for emails, URLs, dates, phone numbers, and IPv4 addresses.
Safe Sandbox Execution
Pure native RegExp engine parsing without unsafe eval() or server transmission.
Frequently Asked Questions
Which JavaScript regex flags are supported?
How are capture groups displayed?
Is it safe to test proprietary data or secrets?
Can catastrophic backtracking freeze my browser?
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