Reels versus regular video posts
Reels links start with instagram.com/reel/, ordinary video posts with /p/. Both are supported, and both return the MP4 that Instagram transcoded. That distinction matters: Instagram re-encodes on upload, so what you download is the platform's highest-quality distribution copy, not the master file sitting on the creator's machine. That ceiling applies to every Instagram downloader — none can serve a file better than the one Instagram itself holds.