Cloud PBX is a service that provides the functions of a traditional office-installed PBX (Private Branch Exchange) in the cloud. Since it operates via the internet, extension calls and external calls can be made from any location: the office, home, or on the go. Because it does not assume a desk phone at every seat, it is often chosen for remote work and for running several sites as one phone system.
The biggest difference from on-premises PBX is the hardware ownership model. On-premises requires purchasing and installing dedicated equipment, which makes the up-front cost substantial, plus self-managed maintenance and upgrades. Cloud PBX is billed monthly according to the number of users or extensions, with no equipment to buy or maintain. Adding or changing locations is usually a matter of a few clicks in a browser-based console, which makes it easier to follow changes in headcount.
Cloud PBX's weakness is its dependence on internet connectivity. If the line or the ISP fails, every call carried over that line stops at once. An on-premises system whose trunks are analog lines or ISDN can still place calls over those lines even when the internet is down. To compensate, redundancy measures such as using mobile lines as backup or contracting with multiple ISPs are recommended. Call quality is also affected by bandwidth and latency, making QoS configuration to prioritize voice packets essential.
Feature-wise, built on VoIP technology, advanced functions like IVR (interactive voice response), CTI (computer telephony integration), call recording, and call analytics are often included as standard, whereas the same functions would require additional investment on an on-premises system. Installing a dedicated app on smartphones turns personal mobile phones into company extensions, so a deployment without company-issued handsets is possible; where staff use their own devices, decide in advance how call logs and contacts will be handled. Combined with virtual phone numbers for business, even more flexible phone environments can be built.
Representative services as of 2026 include Dialpad, RingCentral, Zoom Phone, and Microsoft Teams Phone from overseas vendors, and BIZTEL, MOT/TEL, and Hikari Cloud PBX in Japan. Pricing, integrations, and call-quality characteristics vary by service, so where a trial is offered, testing call quality on the connection you will actually use is the safest way to choose.