H.265, also called HEVC (High Efficiency Video Coding), is the successor to H.264 and the codec that makes high-resolution surveillance affordable at scale. Standardised by ITU-T and ISO/IEC, it delivers roughly the same image quality as H.264 at about half the bitrate — the single biggest lever for cutting storage and bandwidth once cameras move to 4K or a site grows to hundreds of channels.
The savings come from smarter compression: larger, more flexible block partitioning and better prediction let it describe each frame with fewer bits. Vendors layer "smart codec" variants on top (Axis Zipstream, Hikvision H.265+, Dahua Smart H.265) that lower the bitrate further in quiet scenes by spending bits only where there is motion. A 4K camera that needs ~16 Mbps on H.264 may run ~8 Mbps on H.265 for comparable quality.
The cost is compute and compatibility. H.265 decoding is heavier, so a large video wall can stress client machines without hardware decode, and licensing/patent terms are more tangled than H.264's. Some older browsers and clients still lack native support. The pitfall is enabling H.265 on cameras whose viewing clients cannot hardware-decode it — you save disk but overload the operators' screens.
