When building signup forms or user authentication systems, many developers rely on regular expressions (regex) to validate phone numbers. While regex can catch obvious formatting errors, it is far from a complete solution for real-world validation.
A typical regex check might ensure that a phone number contains only digits, plus signs, or dashes. However, this does not verify whether the number actually exists, is active, or can receive messages. Users can still submit fake, recycled, or invalid numbers that pass regex checks without issue.
Another limitation of regex is that it struggles with international numbers. Different countries have different formats, lengths, and dialing rules. Maintaining a comprehensive regex pattern that correctly handles all global cases is extremely difficult and error-prone.
This is why many modern applications are moving toward API-based validation instead. A validation API can not only check formatting but also verify whether a number is valid, active, and reachable. Instead of reinventing the wheel, developers can integrate a dedicated service.
For example, you can use a validation API like CheckNumber: https://www.numberchecker.ai/
to perform real-time phone verification during user signup. This helps reduce fake accounts, improve data quality, and prevent downstream issues caused by bad user data.
Here’s a simple conceptual flow you might follow in your application:
User enters their phone number in your form.
Your backend sends the number to a validation API.
The API returns whether the number is valid, risky, or invalid.
Your app decides whether to accept, warn, or reject the input.
By moving beyond regex and adopting API-based validation, you can build more secure, reliable, and scalable systems that handle real-world data properly.
If you are working on user authentication, onboarding, or data collection, integrating a proper phone validation service is a smart engineering decision.
Top comments (1)
let’s learn from each other and tackle this number verification roadblock together