Phone number regex C#

The regular expressions below can be used to validate if a string is a valid phone number format and to extract a phone number from a string. Please note that this validation can not tell if a phone number actually exists.

The basic international phone number validation

A simple regex to validate string against a valid international phone number format without delimiters and with an optional plus sign:

new Regex("^\\+?[1-9][0-9]{7,14}$")

Test it!

/^\+?[1-9][0-9]{7,14}$/

True

False

Enter a text in the input above to see the result

Example code in C#:

using System.Text.RegularExpressions;
using System.Linq;
                    
public class Program
{
    public static void Main()
    {
        // Validate phone number
        Regex validatePhoneNumberRegex = new Regex("^\\+?[1-9][0-9]{7,14}$");
        validatePhoneNumberRegex.IsMatch("+12223334444"); // returns True
        
        // Extract phone number from a string
        Regex extractPhoneNumberRegex = new Regex("\\+?[1-9][0-9]{7,14}");
        extractPhoneNumberRegex.Matches("You can reach me out at +12223334444 and +56667778888")
            .Cast<Match>()
            .Select(m => m.Value) 
            .ToArray(); // returns {"+12223334444", "+56667778888"}
    }
}

The more complex phone number validation

This regular expression will match phone numbers entered with delimiters (spaces, dots, brackets, etc.)

new Regex("^\\+?\\d{1,4}?[-.\\s]?\\(?\\d{1,3}?\\)?[-.\\s]?\\d{1,4}[-.\\s]?\\d{1,4}[-.\\s]?\\d{1,9}$")

Test it!

/^\+?\d{1,4}?[-.\s]?$?\d{1,3}?$?[-.\s]?\d{1,4}[-.\s]?\d{1,4}[-.\s]?\d{1,9}$/

True

False

Enter a text in the input above to see the result

Example code in C#:

using System.Text.RegularExpressions;
                    
public class Program
{
    public static void Main()
    {
        // Validate phone number
        Regex validatePhoneNumberRegex = new Regex("^\\+?\\d{1,4}?[-.\\s]?\\(?\\d{1,3}?\\)?[-.\\s]?\\d{1,4}[-.\\s]?\\d{1,4}[-.\\s]?\\d{1,9}$");
        validatePhoneNumberRegex.IsMatch("+1 (615) 243-5172"); // returns True
    }
}

Test it!

True

False

Enter a text in the input above to see the result

Extra information about validating phone number

While validation of phone numbers using regex can give a possibility to check the format of the phone number, it does not guarantee that the number exists.

There might be also an option to leave a phone number field without any validation since some users might have:

More complex phone numbers with extensions
The different phone numbers for calling them on a different time of day

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