A standard for physical IP-based security products such as IP CCTV cameras. ONVIF is an acronym for Open Network Video Interface Forum but was originally Open Network Video Interface Forum. The longer name was dropped as the scope of the standard expanded beyond video applications. For the practical application of CCTV ONVIF is a worldwide open standard protocol for interconnection between IP based systems such as video surveillance and access control devices.
As long as an IP CCTV camera is fully ONVIF complaint, one manufacturer's camera should work with another manufacturer's DVR or utilities such as ZoneMinder CCTV Camera Monitoring Software. It is important to ensure am IP based CCTV product is ONVIF complaint or it should otherwise be avoided. When a Network Video Recorder (NVR) sends commands to an IP camera to request high-resolution videos, a common standard enforced by the ONVIF protocol allows to such camera to deliver what was asked even if the NVR was manufactured by another company.
Caution! Be advised that there are several companies online selling through Newegg, Amazon, or Ali Express which sell cheap Chinese made cameras with knockoff chipsets and advertise such as ONVIF compliant when they are only partially or not at all compliant. Even more confusing is that ONVIF has created several profiles that are loosely followed by IP camera chipset manufacturers.
At minimum an ONVIF camera should provide an RTSP stream utilizing a common compression algorithm. Motion detection, audio, remote viewing, camera settings, and PTZ control are features not guaranteed to work on these gray area ONVIF cameras. Do not expect to purchase an ONVIF camera and have it work with a security camera system unless it has been verified to do so by the company you are purchasing it from and vice versa.
Some advanced functions of your IP cameras, such as motion detection, PTZ controls, etc. would not be available with the free version of the ONVIF software. Usually, the third-party ONVIF IP camera software companies require you to pay for a license, so that you can get more advanced features and configure more brands of IP cameras.
Manufactures that offer IP cameras that are 100% compatible with ONVIF Profile S are a good choice. Camera models made by Honeywell, Panasonic, Dynacolor, Sony, Samsung, Pelco, Bosch, Axis and Arecont Vision can be ONVIF compliant but only some of their models, others may not. Keep in mind that ONVIF Profile S compliance may not include motion detection, settings changes, or PTZ control. Camera settings, video analytics, motion detection, and PTZ control are all called "conditional" features in ONVIF Profile S.