Explainers · 4 min read
How Video Compression Works, Explained Simply
Raw video would be enormous. Compression is the reason a two-minute clip fits in a few megabytes instead.
The basic idea
Video compression works by not storing every pixel of every frame from scratch. Instead, it stores a full frame occasionally and, for the frames in between, only the parts of the image that actually changed.
That's why a mostly-static video (a talking head, say) compresses far smaller than fast-moving action footage with lots of frame-to-frame change.
Lossy vs. lossless, in practice
Almost all video you download from social platforms is lossy — some fine detail is discarded to shrink the file, in a way designed to be barely noticeable to the eye at normal viewing distance.
Lossless compression exists but produces far larger files and is mostly used in professional editing workflows, not everyday sharing.
Why re-uploading degrades quality further
Each time a video is compressed again — for instance, downloaded, then re-uploaded to another platform — a little more detail is lost. This is why a video reposted several times across different apps often looks noticeably worse than the original.