2.5th Generation of systems for mobile communications (2.5G) denotes a transitional class of standards that bridged the gap between 2G and 3G by enhancing Second Generation networks with packet-switched data capabilities.
Within the realm of 2.5G, two prominent technologies emerged: GPRS (General Packet Radio Service) extending GSM, and the data-oriented evolution of cdmaOne (IS-95B). These enhancements mark a significant step in mobile communication technology, succeeding the voice-oriented 2G (Second Generation) systems and ushering in the first commercially viable mobile data experience.

2.5G is engineered as an overlay on the existing 2G circuit-switched infrastructure, adding a packet-switched core that enables integration with the Internet Protocol (IP) world and streamlines the delivery of a new class of IP-based services and applications, such as WAP browsing, MMS messaging, and basic email. Depending on the specific 2.5G technology and network configuration in use, it is capable of delivering download speeds ranging from 20 to 40 Kbps. Additionally, 2.5G networks introduced volume-based data charging, replacing the time-based model of voice calls and establishing the commercial foundation later adopted by 3G and 4G.
However, these capabilities, while a substantial improvement over 2G, do not meet the more advanced requirements and standards set by 3G (Third Generation) systems, positioning 2.5G as a
bridging generation rather than a standalone milestone.