Definition
Liveliness
A bundle of real-time signals describing whether a phone number is active, reachable, and safe to use right now.
Liveliness goes beyond checking that a number is well-formed. It resolves, at request time, whether a number is assigned and active on a carrier network, whether it can currently receive a call or SMS, what line type it is, which carrier holds it, and how much fraud risk it carries.
Because it's resolved live rather than read from a cache, liveliness reflects a number's current state — a line disconnected yesterday reads as not live today.
Deep dive: What Is Phone Number Liveliness?