What format do my mobile numbers need to be in to send an SMS?

What is a Mobile Number Format?

A mobile number is unique to a specific subscriber and is essential for identifying the user within the telecommunications network.

The mobile number format refers to the standardized way of presenting a mobile number, ensuring it can be correctly routed, verified and understood across different networks and countries. The most widely recognized and utilized format for mobile numbers is the E.164 format, established by the International Telecommunication Union (ITU).

Some E.164 format norms for international standard phone numbers are:

1. A Plus Sign (+)

Indicates that the number is in international format.

2. Country Code

The numeric prefix representing the country or territory.

3. National Destination Code (NDC)

The code representing the specific region or network within the country.

4. Subscriber Number

The unique identifier for the mobile subscriber.

What format do my mobile numbers need to be in to send an SMS?

Sending SMS effectively requires ensuring that the mobile numbers you're sending to are in the correct format. Improperly formatted numbers can result in failed deliveries, which can be particularly problematic for businesses relying on SMS especially for crucial use cases like SMS verification.

This comprehensive guide will delve into the required format for mobile numbers, with questions and answers to clarify common concerns.

The points to remember when sending SMS:

1. International Format

The E.164 international standard is the recommended format for sending SMS messages globally. It ensures that each number is unique and can be recognized by telecommunications networks worldwide. This format includes a plus sign (+), the country code, and the subscriber number. Adhering to this standard helps avoid common issues with message delivery.

2. Country Code

The country code is a critical component of the international format, identifying the recipient's country. Each country has a unique code, such as +1 for United States and +44 for the United Kingdom.  
Including the correct country code ensures that the SMS system routes the message to the correct geographical region. Without it, the message may not reach its intended destination.

3. Leading Zeros

Leading zeros are typically used in national dialling formats but should be omitted in the international format. When converting a number to the E.164 format, any leading zeros in the national destination code or subscriber number should be removed.  

For example, a UK number like 07912345678 should be formatted as +447912345678 to ensure it adheres to international standards.

4. Special Characters and Spaces

Special characters, spaces, and dashes can interfere with the processing of a mobile number. To ensure successful SMS delivery, the number should be a continuous string of digits which would also help in SMS number authentication. For instance, a number like +44 7912-345-678 should be formatted as +447912345678. This helps avoid routing issues and ensures the number is correctly recognized by the SMS system.

5. Length and Validity

The length of a mobile number, including the country code, varies by country. It is essential to ensure that the number is within the valid length for the specific country.

For example, US numbers typically have 10 digits following the country code, while UK numbers have 10 digits excluding the country code. Ensuring the correct length helps prevent delivery failures and ensures the number's validity.

FAQs

Q1. Why is the country code important in SMS formatting?

A: The country code is essential because it specifies the recipient's country. Without the country code, the SMS system cannot route the message correctly irrespective of it being a personal message or a part of SMS marketing. For example, the country code for the United States is +1, and for the United Kingdom, it is +44.

Q2. Should I include leading zeros in the mobile number?

A: No, you should not include leading zeros in the mobile number when formatting for SMS. Leading zeros are typically part of the national dialling format and are not used in the international format. For example, a UK number that starts with 079 should be formatted as +4479 when sending an SMS.

Q3. Can I use special characters or spaces in the mobile number?

A: No, you should avoid using any special characters, spaces or dashes in the mobile number. The same applies to businesses using WhatsApp accounts for WhatsApp OTPs. For instance, +44 7912 345 678 should be written as +447912345678.

Q4. Give some examples of different number formats of countries?

Some examples of country specific formatting are:

1. United States: +1 (Country Code) + 10-Digit Number (e.g: +12345678900)
2. United Kingdom: +44 (Country Code) + 10-Digit Number (e.g: +447912345678)
3. India: +91 (Country Code) + 10-Digit Number (e.g: +919876543210)
4. Australia: +61 (Country Code) + 9-Digit Number (e.g: +61412345678)

Q5. Are there any other formatting considerations?

Some additional considerations are:

1. Content Templates

When using SMS APIs, ensure the numbers are formatted correctly according to the API documentation and content template restrictions. For example: Verify Now is an OTP service provider helping businesses to easily send OTP SMS with their own registered template.

2. Character Limits

When sending long messages that exceed the standard SMS character limit, they may be sent as concatenated messages. Ensure the numbers are formatted correctly to avoid any issues with message delivery. For example: If sending a concatenated message to a UK number, format it as +447912345678.

3. Compliance with SMS Regulations

Different countries have regulations regarding SMS marketing and communication. Ensure your numbers are formatted correctly to comply with these regulations and avoid penalties. For example: In compliance with SMS regulations for USA, ensure that marketing messages sent to US numbers are formatted as +15551234567.

4. Alphanumeric Sender IDs

Alphanumeric sender IDs allow businesses to send SMS messages using a custom name or a combination of letters and numbers instead of a standard phone number. However, alphanumeric sender IDs cannot receive replies, making them suitable for one-way communication only. Proper use of these IDs can significantly improve the effectiveness of SMS marketing campaigns.

Conclusion

Understanding and correctly formatting mobile numbers is crucial for effective communication in today's interconnected world. By adhering to the E.164 standards and ensuring your numbers are correctly formatted, you can ensure reliable and accurate delivery of calls and messages, whether for personal use or business purposes. Proper formatting also enhances compatibility with various systems and APIs, supporting seamless integration and operation across different platforms.