Pinch zoom on UI

Hey. Hope this works for you:

 using UnityEngine;
 
 public class PinchZoom : MonoBehaviour
 {
     public Canvas canvas; // The canvas
     public float zoomSpeed = 0.5f;        // The rate of change of the canvas scale factor
     
     void Update()
     {
         // If there are two touches on the device...
         if (Input.touchCount == 2)
         {
             // Store both touches.
             Touch touchZero = Input.GetTouch(0);
             Touch touchOne = Input.GetTouch(1);
 
             // Find the position in the previous frame of each touch.
             Vector2 touchZeroPrevPos = touchZero.position - touchZero.deltaPosition;
             Vector2 touchOnePrevPos = touchOne.position - touchOne.deltaPosition;
 
             // Find the magnitude of the vector (the distance) between the touches in each frame.
             float prevTouchDeltaMag = (touchZeroPrevPos - touchOnePrevPos).magnitude;
             float touchDeltaMag = (touchZero.position - touchOne.position).magnitude;
 
             // Find the difference in the distances between each frame.
             float deltaMagnitudeDiff = prevTouchDeltaMag - touchDeltaMag;
 
             // ... change the canvas size based on the change in distance between the touches.
             canvas.scaleFactor -= deltaMagnitudeDiff * zoomSpeed;
 
             // Make sure the canvas size never drops below 0.1
             canvas.scaleFactor = Mathf.Max(canvas.scaleFactor, 0.1f);
         }
     }
 }

I just slightly edited the original tutorial source code. Remember to assign the canvas in the inspector. You may have to play around with the numbers ;)