How Do You Validate International Phone Numbers?
Posted: Tue May 27, 2025 9:03 am
Validating international phone numbers is crucial for ensuring that contact information is accurate, formatted correctly, and usable for communication across different countries. Unlike domestic phone numbers, international numbers vary widely in format, length, and numbering rules, so validation requires a structured approach. Below is a detailed overview of how to validate international phone numbers effectively.
1. Understand the Structure of International Phone Numbers
International phone numbers typically follow the E.164 standard, which is a globally recognized format defined by the International Telecommunication Union (ITU). The E.164 format includes:
A plus sign (+) indicating an international number
The country code (1 to 3 digits)
The national destination code (area or operator code)
The subscriber number
For example, a U.S. number in E.164 format looks like: +14155552671
Validating international numbers involves confirming adherence to this recent mobile phone number data standard or similar regional formats.
2. Steps to Validate International Phone Numbers
a. Normalization
Remove all formatting characters such as spaces, parentheses, dashes, and dots.
Ensure the phone number starts with a plus sign (+) followed by the country code.
If the number lacks a plus sign but you know the country, prepend the country code.
Example: Convert (415) 555-2671 to +14155552671.
b. Check Country Code
Extract the country code (the digits following the plus sign).
Verify if the country code is valid by comparing it to a list of assigned codes maintained by the ITU.
Reject numbers with invalid or nonexistent country codes.
c. Length Validation
Each country has specific length requirements for phone numbers, including the national destination code and subscriber number.
Validate that the number of digits (excluding the plus and country code) falls within the acceptable range for that country.
Numbers that are too short or too long are invalid.
d. Format Validation Using Libraries
Manual validation can be error-prone due to country-specific rules and exceptions. Instead, use specialized phone number validation libraries such as:
Google’s libphonenumber (available in Java, Python, JavaScript, and other languages)
These libraries can:
Parse numbers into components
Validate if the number is possible and valid for the country
Identify number types (mobile, landline, toll-free)
Format numbers into standard representations
Example in Python using libphonenumber:
python
Copy
Edit
import phonenumbers
from phonenumbers import NumberParseException, is_valid_number
try:
number = phonenumbers.parse("+14155552671")
if is_valid_number(number):
print("Valid international phone number")
else:
print("Invalid number")
except NumberParseException:
print("Error parsing the number")
e. Real-Time Validation with APIs
For the highest accuracy, especially in business or telecom applications, you can use real-time validation services such as:
Twilio Lookup
NumVerify
Next Caller
These APIs check if a number is currently active, assigned, or disconnected, and often provide additional info like carrier and line type.
3. Common Challenges
Number portability: A phone number may move from one carrier or region to another, complicating validation.
New or changed numbering plans: Countries periodically update numbering rules.
Spoofed or fake numbers: Validation tools can help detect these but cannot guarantee 100% prevention.
1. Understand the Structure of International Phone Numbers
International phone numbers typically follow the E.164 standard, which is a globally recognized format defined by the International Telecommunication Union (ITU). The E.164 format includes:
A plus sign (+) indicating an international number
The country code (1 to 3 digits)
The national destination code (area or operator code)
The subscriber number
For example, a U.S. number in E.164 format looks like: +14155552671
Validating international numbers involves confirming adherence to this recent mobile phone number data standard or similar regional formats.
2. Steps to Validate International Phone Numbers
a. Normalization
Remove all formatting characters such as spaces, parentheses, dashes, and dots.
Ensure the phone number starts with a plus sign (+) followed by the country code.
If the number lacks a plus sign but you know the country, prepend the country code.
Example: Convert (415) 555-2671 to +14155552671.
b. Check Country Code
Extract the country code (the digits following the plus sign).
Verify if the country code is valid by comparing it to a list of assigned codes maintained by the ITU.
Reject numbers with invalid or nonexistent country codes.
c. Length Validation
Each country has specific length requirements for phone numbers, including the national destination code and subscriber number.
Validate that the number of digits (excluding the plus and country code) falls within the acceptable range for that country.
Numbers that are too short or too long are invalid.
d. Format Validation Using Libraries
Manual validation can be error-prone due to country-specific rules and exceptions. Instead, use specialized phone number validation libraries such as:
Google’s libphonenumber (available in Java, Python, JavaScript, and other languages)
These libraries can:
Parse numbers into components
Validate if the number is possible and valid for the country
Identify number types (mobile, landline, toll-free)
Format numbers into standard representations
Example in Python using libphonenumber:
python
Copy
Edit
import phonenumbers
from phonenumbers import NumberParseException, is_valid_number
try:
number = phonenumbers.parse("+14155552671")
if is_valid_number(number):
print("Valid international phone number")
else:
print("Invalid number")
except NumberParseException:
print("Error parsing the number")
e. Real-Time Validation with APIs
For the highest accuracy, especially in business or telecom applications, you can use real-time validation services such as:
Twilio Lookup
NumVerify
Next Caller
These APIs check if a number is currently active, assigned, or disconnected, and often provide additional info like carrier and line type.
3. Common Challenges
Number portability: A phone number may move from one carrier or region to another, complicating validation.
New or changed numbering plans: Countries periodically update numbering rules.
Spoofed or fake numbers: Validation tools can help detect these but cannot guarantee 100% prevention.