Optimize your mobile game performance: Expert tips on graphics and assets

Disable unnecessary Player or Quality settings

In the Player settings, disable Auto Graphics API for unsupported platforms to prevent generating excessive shader variants. Disable Target Architectures for older CPUs if your application is not supporting them.

In the Quality settings, disable needless Quality levels.

Disable unnecessary physics

If your game is not using physics, uncheck Auto Simulation and Auto Sync Transforms. These will just slow down your application with no discernible benefit.

Choose the right frame rate 

Mobile projects must balance frame rates against battery life and thermal throttling. Instead of pushing the limits of your device at 60 fps, consider running at 30 fps as a compromise. Unity defaults to 30 fps for mobile.

You can also adjust the frame rate dynamically during runtime with Application.targetFrameRate. For example, you could drop below 30 fps for slow or relatively static scenes and reserve higher fps settings for gameplay.

Avoid large hierarchies

Split your hierarchies. If your GameObjects do not need to be nested in a hierarchy, simplify the parenting. Smaller hierarchies benefit from multithreading to refresh the Transforms in your scene. Complex hierarchies incur unnecessary Transform computations and more cost to garbage collection.

See Optimizing the Hierarchy and this Unite talk for best practices with Transforms. 

Transform once, not twice

Additionally, when moving Transforms, use Transform.SetPositionAndRotation to update both position and rotation at once. This avoids the overhead of modifying a transform twice.

If you need to Instantiate a GameObject at runtime, a simple optimization is to parent and reposition during instantiation:

GameObject.Instantiate(prefab, parent);

GameObject.Instantiate(prefab, parent, position, rotation);

For more details about Object.Instantiate, please see the Scripting API.

Assume Vsync is enabled 

Mobile platforms won’t render half-frames. Even if you disable Vsync in the Editor (Project Settings > Quality), Vsync is enabled at the hardware level. If the GPU cannot refresh fast enough, the current frame will be held, effectively reducing your fps. 

Source: Unity Technologies Blog