How To Normalize International Phone Numbers For WhatsApp

Want your WhatsApp messages to land every time? Save each contact phone number in the right format. WhatsApp only recognises numbers written in full international style: a plus sign, the country code, and the cleaned-up local number. Plus, in certain countries, there are some number normalization ambiguities, like adding or removing a digit — getting them wrong means the chat never starts or your API call fails.

Learn how to validate and format phone numbers for Mexico, Argentina, Brazil and Russia.

Normalize phone numbers by country

Mexico

Write +52 1 before the 10-digit mobile number. Example: +52 1 55 1234 5678 WhatsApp still uses the “1” to mark mobiles, even after Mexico’s 2019 dial-plan change.

If the local number starts with 11, drop those first two digits. Old Telcel/Nextel quirks; keeps the total length correct.(green-api.com) Final WhatsApp ID: 521XXXXXXXXXX@c.us Required by most BSPs and the Business API.

Heads-up: For voice or SMS outside WhatsApp you now dial +52 XXXXXXXXXX without the “1”. Some providers block the old format.

Argentina

Put a 9 after the country code: +54 9. The “9” flags mobiles in Argentina. Delete the 15 that often appears at the start of local mobile numbers. “15” is a national prefix not used internationally.

Your WhatsApp ID ends up as 549XXXXXXXXXX@c.us (13 digits total). Required for message delivery.

Brazil

For area codes 11–19, 21, 22, 24, 27, 28, add a 9 in front of the local number. Example: +55 21 98765 4321 ANATEL added a ninth digit to mobiles in these regions.

For most other area codes, keep the number as is (already 9 digits). Not every DDD needed the extra “9”.

WhatsApp IDs are either 55DD9XXXXXXXX@c.us or 55DDXXXXXXXX@c.us (12–13 digits). Both forms are accepted once the rule above is applied.

Russia

Replace the domestic “8” with +7. Example: 8 912 345 6789 → +7 912 345 6789 “8” is only a national trunk prefix; WhatsApp needs the international code.

Make sure you end up with 11 digits after the plus sign. Russia’s numbers are “+7” plus ten digits. WhatsApp ID looks like 7XXXXXXXXXX@c.us (no plus). That’s the format the API expects.

Quick tips

Strip spaces, dashes and brackets before you store the number.
Use a phone-parsing library (e.g., Google’s libphonenumber) to automate clean-up.
Test a sample number with https://wa.me/ <phonenumber> Before sending the messages

Wassenger gives superpowers to your WhatsApp

Wassenger’s API formats, validates and verifies WhatsApp phone numbers for you before you send the message, so you can plan ahead before communicating with your clients. Explore a free 7-day trial and see it work before your coffee gets cold. 😉