How to Choose the Best Phone Validation API for Your Business

In today’s world, accurate and reliable phone validation is crucial for businesses across various industries. From avoiding junk data entry to preventing fraud and abuse, a phone validation tool is important for any business to incorporate as part of its workflow. However, not all phone validation APIs are created equal. In this comprehensive guide, we will delve into the key criteria that go beyond the basic syntax and number block checks, exploring ported carrier assignment, distinguishing between fixed and non-fixed VoIPs, evaluating latency, enterprise-grade availability, and more.

Validity Beyond Numbering Plan

  • Ported Carrier Assignment: A reliable phone validation API should not stop at a syntax check or seeing if the number is within the NANPA numbering block. While the numbering block checks confirm that the number is within a block assigned to a carrier at some point, this simple check doesn’t confirm the number is active or confirm the current carrier holding this number. Instead, it should identify the accurate ported carrier data holding that number in real-time. This additional layer ensures a more accurate understanding of the phone number’s real-time status.
  • Connected/Disconnected Status: Further, the phone validation API must be capable of determining the connected or disconnected status of a number. Merely knowing the carrier information is insufficient because the number might not be assigned to a subscriber, or the number is currently disconnected. This information is vital for businesses to avoid junk data input, improve contactability, and keep carriers from marking businesses as spam by calling inactive or disconnected numbers.

MVNO Carriers and Non-fixed VoIP Identification

  • VoIP Recognition: A good phone validation API should recognize the line type of a number beyond landline and mobile. That should include VoIP, premium, and toll free line types so businesses can prioritize the leads and signups with a comprehensive view of the phone number. That helps with filtering rules based on line types rather than checking for every carrier, given there are thousands in the U.S. 
  • MVNO Carrier Recognition: Similarly, it’s essential to recognize and validate numbers associated with MVNO (Mobile Virtual Network Operator) carriers, such as Google Voice, Twilio, etc. These carriers lease spectrum from other telecom providers; thus, it is important to know who the eventual carrier is holding the number currently. For example, certain carriers will return a Skype voice number as Level 3 communications (and the line type as landline) because they are the carrier subleasing the spectrum to Skype. Businesses should verify if this MVNO level fidelity is provided, and numbers like Skype voice are accurately identified along with non-fixed VoIP as the line type (more below). 
  • Non-fixed VoIP Recognition: While many phone validation APIs recognize VoIP phones that are delivering the service over the internet, they do not further differentiate between a Comcast phone provider that businesses and homes use for legitimate purposes and a Skype, Twilio, or Pinger number, which are used from anywhere in the world and are associated with spam and abuse. Hence, it is critical that the provider differentiates between these line types appropriately so that simple filtering rules can be written and avoid false positives. 

Coverage and Accuracy

  • Real-Time Data: The NANPA numbering block data is available via files and doesn’t change often. Because of that, the data is stale and doesn’t account for ported data or current phone activity. A good phone validation API provider should be able to provide data as close to real-time as possible and take into account the latest ported data or phone activity signals, especially for fraud and abuse use cases. 
  • Phone Activity Coverage: A phone validation API should also excel in accurately identifying the status of phone numbers. As part of the evaluation, businesses should check the data sources. If it only comes from carriers, it is incomplete data because not all share that data, impacting coverage. It also adds to the latency of the APIs, as some of this carrier data is pretty slow to retrieve. 

Response Times and Enterprise-Grade Availability at Scale

  • Low Latency APIs: An effective phone validation API is low latency at any scale, ensuring seamless integration into various mission-critical business processes. While evaluating the provider on latency, it is important to not only check the average response times, but also P95 (response time of 95% of the queries) at a minimum to ensure they fit in within the business needs. 
  • Enterprise-Grade Availability: The API must demonstrate high availability at scale, catering to the needs of enterprise businesses. Downtime can be costly, so reliability is non-negotiable.


  • Transparent and Competitive: Pricing should be transparent and competitive, especially required at scale. An ideal API provider should offer flexible pricing models accommodating different business needs.

In conclusion, phone validation has quite a few nuanced checks extending beyond basic phone validity. Trestle’s Phone Validation API stands out by addressing ported carrier assignment, high coverage activity status, non-fixed VoIP identification, and MVNO carrier recognition. In addition, Trestle’s Phone Validation API is low latency and scalable, able to serve any business size and need.

If you want to learn more about our Phone Validation API, feel free to look at our API Documentation or contact us