Disabling Fullscreen

When I test my game on Unity Remote it stretches it to fill the whole screen, since my game is pixel art it makes it look awful. Does anybody know how I can put black borders so it can maintain it’s aspect ratio(5 ,9)?

The purpose of Unity Remote is to allow you to test device input quickly (without having to build the app). For rendering it simply displays everything that is visible in the editor. You would have to choose the same aspect ratio in the editor’s game view as your device and then add then scale your content appropriately.
For testing your content on mobile devices you can also take a look at the device simulator package Introduction | Device Simulator | 2.2.4-preview It might be more useful than the Unity Remote for you.

Thankyou