No Caller ID is a telecommunications feature that allows a caller to deliberately hide their phone number and identity from the recipient's caller ID display. When a call is made with No Caller ID, the recipient sees messages like "No Caller ID," "Private Number," or "Unknown Caller" instead of the caller's actual phone number. This is done by blocking or withholding the caller ID information during the call setup process

. There are several ways No Caller ID can be activated:

• Dialing a special prefix before the number (e.g., *67 in the U.S. or 141 in the U.K.) to block caller ID for that specific call.
• Changing phone settings to hide caller ID for all outgoing calls.
• Using carrier services that permanently block caller ID.
• Using VoIP services that allow caller ID hiding via app settings

The purpose of No Caller ID is often to maintain privacy or anonymity, such as when individuals want to keep their number private or when organizations want to avoid return calls. However, it can also be exploited by telemarketers, scammers, or fraudsters to conceal their identity

. It is important to distinguish No Caller ID from "Unknown Caller." No Caller ID means the caller intentionally blocked their information, while Unknown Caller usually means the phone service provider could not identify the caller due to technical or network issues

. In summary, No Caller ID calls are those where the caller has deliberately hidden their phone number to maintain privacy or anonymity, and the recipient cannot see the caller's number on their device