Regex Tester

Free Online Regex Tester

Regular expressions (regex) are patterns used to match character combinations in strings. This tool lets you write, test, and debug regex patterns instantly with real-time match highlighting.

Why Use a Regex Tester?

• Instantly see which parts of your text match the pattern
• View capture groups and their values
• Test replace operations before using them in code
• Debug complex patterns step by step
• Learn regex with the built-in cheat sheet

JavaScript Regex Examples

// Test a pattern
const regex = /(\w+)@(\w+)\.(\w+)/g;
const text = "user@example.com";
const matches = text.matchAll(regex);

for (const match of matches) {
  console.log(match[0]); // Full match: user@example.com
  console.log(match[1]); // Group 1: user
  console.log(match[2]); // Group 2: example
  console.log(match[3]); // Group 3: com
}

// Replace with groups
const result = text.replace(regex, '$1 [at] $2 [dot] $3');
// → "user [at] example [dot] com"

Common Regex Patterns

• /^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$/ — Email validation
• /^https?:\/\/[^\s]+$/ — URL validation
• /^\d{4}-\d{2}-\d{2}$/ — Date format (YYYY-MM-DD)
• /^(?=.*[a-z])(?=.*[A-Z])(?=.*\d).{8,}$/ — Strong password
• /^\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}$/ — IPv4 address

Regex Flags Explained

• g (Global) — Find all matches, not just the first
• i (Case-insensitive) — Match regardless of case
• m (Multiline) — ^ and $ match start/end of each line
• s (Dotall) — . matches newline characters
• u (Unicode) — Enable full Unicode matching

Frequently Asked Questions