Glossary
What is caller ID?
Definition
Caller ID is a telephone feature that displays the phone number—and often the name—of an incoming caller before the call is answered. The information is transmitted by the phone network to the recipient's device or system. Caller ID helps people and businesses decide how to handle a call and is widely used for screening and routing.
01How caller ID works
When a call is placed, the network passes along the originating number, and a separate lookup can attach a name (often called CNAM). The receiving phone or system displays this information as the call rings. In business systems, the same data can drive automatic routing, screen pops with customer records, or call whispers for the agent.
02Uses and limitations
Businesses use caller ID to screen calls, prioritize known customers, and personalize greetings. However, the displayed number can be spoofed or falsified by bad actors, so caller ID is not a reliable proof of identity on its own. Verification frameworks have been introduced to help combat spoofing, but caution is still warranted.
03Caller ID and privacy
Callers can often block their number from being displayed, in which case the recipient sees a private or unknown indicator. Businesses set an outbound caller ID that appears when they call others, and choosing a consistent, recognizable number can improve answer rates. Rules governing caller ID display and blocking vary by region.
Frequently asked questions
Can caller ID be faked?
Yes—caller ID can be spoofed to show a false number or name, so it should not be treated as reliable proof of who is calling.
Why does some caller ID show a number but no name?
The name comes from a separate lookup (CNAM) that isn't always available, so a call may display a number without an associated name.
See also
Related terms
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