Great news for users of iPhones 6 and high-res Android devices, which previously upscaled images from 640 pixels square. That size is still perfectly optimized for older iPhone models, though, so I’m curious about whether they’re sending different sizes of images to different devices. Instagram hasn’t released any information about the change beyond a tweet, but I’ve reached out to Mike Krieger and will update this if he responds.
Interestingly, while the 1080 pixel size seems perfectly optimized for the 1080 × 1920 pixel iPhone 6 Plus, that device typically upscales content to the 1242 pixel (414 point) rendering size it uses, then downscales to fit the actual display pixels. If you’re on an iPhone 6 Plus and you can think of a way to test whether this is the case, please let me know what you find.