The process of reducing video file size while preserving as much visual quality as possible.
Video compression reduces the amount of data needed to represent a video, making files smaller for storage and faster to transmit over networks. Uncompressed video is impractically large — a single minute of raw 1080p footage takes up around 10 GB. Compression algorithms identify and remove redundant information, reducing that to megabytes instead of gigabytes. It is the same principle as summarizing a long report: you keep the essential information and cut what is repetitive.
Video compression comes in two varieties: lossless and lossy. Lossless compression preserves every pixel exactly, which is useful for archiving but only achieves modest size reductions (perhaps 2:1). Lossy compression discards information that the human eye is less likely to notice, achieving compression ratios of 50:1 to 1000:1.
Lossy compression exploits how human vision works. We are more sensitive to changes in brightness than color, so codecs can store color information at lower resolution. We are less sensitive to fine detail during fast motion, so codecs allocate fewer bits to high-motion scenes. And because consecutive video frames are mostly identical, codecs store only the differences between frames rather than each frame independently.
The quality of compression depends on the codec used (H.264, H.265, AV1), the bitrate allocated, and the encoding settings. More aggressive compression means smaller files but more visible artifacts — blocky edges, blurring during motion, or color banding in gradients. The goal is to find the sweet spot where the file is small enough for efficient delivery but the artifacts are imperceptible to viewers.
Compression is what makes video on the internet possible. Without it, a 10-minute video would require gigabytes of bandwidth per viewer, making streaming impractical for anyone without a fiber connection. Good compression means faster load times, less buffering, lower bandwidth costs, and the ability to serve viewers worldwide regardless of their connection speed.
host.video applies optimized compression during automatic transcoding, balancing quality and file size for each resolution level. Variable bitrate encoding allocates more data to visually complex scenes and less to simple ones, so every video looks its best at the smallest practical file size.