Choose codecs and bitrates based on device compatibility and network conditions. H.264 (AVC) with AAC audio remains the safest broad-compatibility option; H.265 (HEVC) reduces bandwidth for the same quality but requires compatible devices. For 720p use ~2.5–4 Mbps, 1080p ~5–8 Mbps, and 4K 15–25 Mbps. Use adaptive bitrate (ABR/HLS) to serve multiple qualities and avoid constant buffering.