In plain English
An NVR is the storage heart of an IP-based CCTV system. Cameras send their video stream over the network to the NVR, which records it to an internal hard drive. Unlike older DVR systems that required proprietary coaxial cable, an NVR works over your existing network infrastructure and can be managed remotely. How long footage is retained depends on the NVR's storage capacity and the recording resolution you configure.
Full definition
NVRs have largely replaced DVRs (Digital Video Recorders) in modern commercial CCTV deployments. DVRs used analogue cameras and proprietary cabling; NVRs use IP cameras over standard Cat5e/Cat6 Ethernet, making them easier to integrate with existing IT infrastructure and to manage remotely.
Key NVR considerations include storage capacity (calculated from the number of cameras, resolution, frame rate, and required retention period), redundancy options (RAID or off-site cloud backup), and remote access capabilities for reviewing footage from any device.
Ubiquiti UniFi Protect uses a dedicated NVR appliance (or a UniFi Dream Machine with NVR functionality) to store footage from all UniFi cameras. The system is managed entirely through the UniFi Protect application and does not require a mandatory cloud subscription for local recording.