Regex Tester for C# / .NET Developers

using System.Text.RegularExpressions;

// Compiled regex for performance
var emailRe = new Regex(@"^[w.%+-]+@[w.-]+.[A-Za-z]{2,}$",
    RegexOptions.Compiled | RegexOptions.IgnoreCase);

Console.WriteLine(emailRe.IsMatch("user@example.com")); // True

// Named groups
var logRe = new Regex(@"(?<date>\d{4}-\d{2}-\d{2}) (?<level>ERROR|INFO) (?<msg>.+)");
var m = logRe.Match("2026-04-13 ERROR Something broke");
if (m.Success) {
    Console.WriteLine($"{m.Groups["level"]} — {m.Groups["msg"]}");
}

// Replace
string result = Regex.Replace("hello world", @"\b\w", c => c.Value.ToUpper());