Local number portability for fixed lines, and full mobile number portability for mobile phone lines, refers to the ability of a "customer of record" of an existing fixed-line or mobile telephone number assigned by a local exchange carrier to reassign the number to another carrier ("service provider portability"), move it to another location ("geographic portability"), or change the type of service ("service portability").

Mobile number portability enables mobile phone users to retain a mobile telephone number when changing the mobile network operator.