A VoIP phone or application may have many features an analog phone doesn't support, such as e-mail-like IDs for contacts that may be easier to remember than names or phone numbers, or easy sharing of contact lists among multiple accounts. Generally the features of VoIP phones follow those of Skype and other PC-based phone services, which have richer feature sets but may experience latency-related problems because they rely on mainstream operating systems' IP and audio support.

As mainstream operating systems became better at voice applications with appropriate quality of service (QoS) guarantees and 5G handoff (IEEE 802.21 etc.) becomes available from wireless carriers, tablets and smartphones became the dominant interfaces. iPhone, Android and the QNX OS used in 2012-and-later BlackBerry phones are widely capable of VoIP performance. They also typically support the USB but not Ethernet or Power over Ethernet interfaces. The smartphone became the dominant VoIP phone because it works both indoors and outdoors and shifts base stations/protocols easily to trade off access costs and call clarity and other factors personal to the user, and the PoE/USB VoIP phone was thus the transitional device.

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