When you try photos and other media on Instagram, the standard bright white layout can literally be a blot, especially in dimly lit environments where the bleached interface fades. Luckily, there's a free tweak that you can install to enable the dark mode in the Instagram app for the iPhone. Of course there is a catch: this mod only works if your iPhone is jailbroken.
The built-in "Smart Invert" feature in iOS 11 and above gives you a pseudo-dark mode in Instagram, but the colors in the photos and videos are also adjusted, which does not lead to a good experience. Fortunately, there is a steady jailbreak for iOS 11, so we can force Instagram into an eye-friendly dark mode.
IGDarkMode, by developer Chloe Kuznetsov, is pretty easy to install and activate. Best of all, you do not have to install an external repo in Cydia to get the optimization.
: Install IGDarkMode
Grab your iPhone and open Cydia to get started, then tap the magnifying glass icon on the bottom right to access the search feature. Type "igdarkmode" in the search bar, and then tap optimization as it appears in the results panel.