Abstract: As physical media declines and streaming quality fragments, the "Remux" has emerged as the definitive format for preserving the exact audio-visual quality of a Blu-ray or UHD disc. This paper defines a Remux, contrasts it with encodes and ISOs, details technical specifications, and provides actionable guidelines for storage, playback, and acquisition. 1. Definition & Core Principles A Remux (remultiplex) is a lossless container transformation. It takes the raw video, audio, and subtitle streams from a commercial disc (e.g., Blu-ray, UHD) and repackages them into a more flexible container—typically MKV (Matroska) without any transcoding.