Unity CPU Optimizations

Use magnitude instead of sqr for distance checking

Vector3 pos1;
Vector3 pos2;

float distance1 = Vector3.Distance(pos1, pos2);
float distance2 = (pos1 - pos2).magnitude; // same result as distance1

// For a distance check this is the fastes way
float distance3 = (pos1 - pos2).sqrMagnitude; // result is distance1 * distance1

Cache transform

Cache transform on awake or start.

using UnityEngine;

public class Example : MonoBehaviour
    Transform trans = null;

    // Start function
    void Start()
        trans = transform;

    // Update function
    void Update()
        trans.position = new Vector3(0.0f, 0.0f, 0.0f);

Vector math optimization

Vector3 oldPos; // old position
Vector3 dir; // movement direction
float speed; // movement speed
float input; // input factor

// This is slow
Vector3 pos = oldPos + dir * speed * input * Time.deltaTime;

// This is faster, because only one factor is used
Vector3 pos = oldPos + dir * (speed * input * Time.deltaTime);

// This inlining is the fastes
Vector3 pos = oldPos;
float factor = speed * input * Time.deltaTime;
pos.x += dir.x * factor;
pos.y += dir.y * factor;
pos.z += dir.z * factor;

Cache Time.deltaTime

Cache Time.deltaTime once per frame so you don't have to call into the c++ side of Unity.

Don't move static objects

Don't move Rigedbodies via transform

Use local position and rotation

Inline functions

If before 4.6 runtime manually. After via attribute.

using UnityEngine;
using System.Runtime.CompilerServices;

public class Example : MonoBehaviour
    void Function()


Use string builder

Use shorts and unigned for network communication

Use Unity C# Job System

Reduce generated garbage for the gc

Use subcanvases

Don't use animators for UI

Use a tween system.

Avoid layout groups

If this is not possible use a canvas for this part of the UI.

Use il2cpp instead of mono

Use observer pattern for UI instead of updating it every frame

Don't update every system every frame

Use different tick rates for different systems if possible.

Use instancing

Try to get away with mobile shaderes

Don't use foreach

Don't use linq

Use id version of Animator, Material and Shader functions

Don't use string versions. The id can be cashed at awake or start.

From 5.3 on use non-alloc versions of RaycastAll and Spherecast

Avoid null checks of MonoBehaviour in hotpasse code

Unity goes into c++ side for this operation.

Use the min length and mask for raycasts

Use one dim arrays

float[] best;
float[][] good;
float[,] worst;

Use an UpdateManager instead of the MonoBehavior Update function

Cache Vectors like Vector3.zero and Quatornion.identity

Unity creates a new Vector every time it's practically like new Vector3(0, 0, 0). Use static readonly because Vectors can't be const.

Don't use enums as keys for dictionaries

Cach array that comes from Unity (f. e. mesh.verticies)

Unity creates them new every time you access them.

Avoid slow string API functions

Make your own. This can be up to 10 or even 100 times faster.

Parse json and xml files on worker threads if no Unity type is part of them

Use module for selecting frame you want to wo some stuff

This is usefull for AI and other systems.

using UnityEngine;

public class Example : MonoBehaviour
    int interval = 3;

    void Function()
        if(Time.frameCount % interval == 0)
            // Do some stuff every 3rd frame
        else if (Time.frameCount % interval == 1)
            // Do some stuff every 3rd frame but on the second frame

Parent GameObjects on instantiate not seperate afterwards

Use structs instead of classes

Structs are created on the stack not on the heap.

Use the compare tag function not ==

Use Set function of a Transform only once per frame per object

Change the physics timestep to the slowest you can get away with

Don't use OnInside callback for a collider

Use layers instead of tags

Combine meshes to reduce draw calls

This can be done with an editor tool.

Bake textures into atlases

The function Texture2D.PackTextures can bake multiple textures into an atlas.

Remove raycaster on non interactable canvases

Disable raycast target on UI.Images if it's not interactable

You can disable nullcheckers and array boundrary checkers in il2cpp

Use the attributis inside the Il2cppSetOptionAttribute.cs file.

Remove animation settings if not needed

This will reduce memory and loading time.

Don't use humanoid animation settings if not needed

Only use humanoid animation settings if you need inverse kinematic or animation retargeting. Use generic instead.

Enable Animator.keepControllerStateOnDisable if you disable GameObjects with an animator on it (available 2018.1+)

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