How to Validate Phone Numbers Using Regex

Phone number validation is a common task in many applications. Whether it's for user registration, form submissions, or data processing, ensuring that the phone number is in the correct format is important.

What is Regex?

Regex, short for Regular Expression, is a sequence of characters that defines a search pattern. It is commonly used for pattern matching and validation tasks. In the context of phone number validation, regex allows us to define a specific pattern that the phone number must match.

Phone Number Formats

Before we dive into writing the regex for phone number validation, let's understand the different formats that we want to validate:

  • 1-234-567-8901
  • 1-234-567-8901 x1234
  • 1-234-567-8901 ext1234
  • 1 (234) 567-8901
  • 1.234.567.8901
  • 1/234/567/8901
  • 12345678901

Regex Pattern for Phone Number Validation

Now that we know the different phone number formats, let's create a regex pattern to validate them. Here's a regex pattern that can handle all the mentioned formats:


This regex pattern breaks down as follows:

  • ^ - Start of the string
  • (1[-.\/]?)? - Optional "1" followed by an optional hyphen, dot, or forward slash
  • (\()? - Optional opening parenthesis
  • \d{3} - Three digits (area code)
  • (\))? - Optional closing parenthesis
  • [-.\/]? - Optional hyphen, dot, or forward slash
  • \d{3} - Three digits
  • [-.\/]? - Optional hyphen, dot, or forward slash
  • \d{4} - Four digits
  • \s?(ext|x)\d{4} - Optional space followed by "ext" or "x" and four digits
  • $ - End of the string

This pattern allows for flexibility while validating the phone number. It can handle variations in spacing, parentheses, and extensions.

Using the Regex Pattern

Now that we have our regex pattern, let's see how we can use it in different programming languages.


Here's an example of using the regex pattern in JavaScript:

        const phoneNumberRegex = /^(1[-.\/]?)?(\()?\d{3}(\))?[-.\/]?\d{3}[-.\/]?\d{4}(\s?(ext|x)\d{4})?$/;
        const phoneNumber = "1-234-567-8901";

        if (phoneNumberRegex.test(phoneNumber)) {
            console.log("Phone number is valid");
        } else {
            console.log("Phone number is invalid");


In Python, we can use the re module to work with regex. Here's an example:

        import re

        phoneNumberRegex = r"^(1[-.\/]?)?(\()?\d{3}(\))?[-.\/]?\d{3}[-.\/]?\d{4}(\s?(ext|x)\d{4})?$"
        phoneNumber = "1-234-567-8901"

        if re.match(phoneNumberRegex, phoneNumber):
            print("Phone number is valid")
            print("Phone number is invalid")


Validating phone numbers using regex is a powerful technique for ensuring that the phone numbers entered in your application are in the correct format. By defining a specific pattern using regex, you can easily validate phone numbers with different formats.

Remember to use the regex pattern ^(1[-.\/]?)?(\()?\d{3}(\))?[-.\/]?\d{3}[-.\/]?\d{4}(\s?(ext|x)\d{4})?$ to validate phone numbers in your application. The provided code examples in JavaScript and Python should help you get started with implementing phone number validation.