Progressive scan means every frame of video is stored and shown as one complete image. The first line of pixels, then the second, then the third — all in one pass. This is how essentially everything on the modern internet, in gaming and in cinema works: 1080p, 4K UHD, 8K — the "p" stands for progressive.
The opposite is interlaced scan, where each frame is split into two half-images (fields) — odd lines and even lines — captured a fraction of a second apart and shown alternately. Interlaced was invented in the 1940s to halve the bandwidth needed to broadcast television over the air. It worked well for the chunky CRT TVs of the time, but on modern flat-panel displays it produces "combing" artefacts on motion and needs an extra processing step (deinterlacing) to look right.
Why this matters in 2026: every modern streaming pipeline assumes progressive video. The only real reason to handle interlaced footage today is when you're working with legacy broadcast material (old TV archives, vintage DVDs, satellite feeds in some countries). If you're starting a new project, capture and store progressive — it's simpler, plays correctly everywhere and compresses better.
