EventSystem.IsPointerOverGameObject

Parameters

Description

Is the pointer with the given ID over an EventSystem object?

using UnityEngine;
using System.Collections;
using UnityEngine.EventSystems;

public class MouseExample : MonoBehaviour
{
    void Update()
    {
        // Check if the left mouse button was clicked
        if (Input.GetMouseButtonDown(0))
        {
            // Check if the mouse was clicked over a UI element
            if (EventSystem.current.IsPointerOverGameObject())
            {
                Debug.Log("Clicked on the UI");
            }
        }
    }
}

If you use IsPointerOverGameObject() without a parameter, it points to the "left mouse button" (pointerId = -1); therefore when you use IsPointerOverGameObject for touch, you should consider passing a pointerId to it.

using UnityEngine;
using System.Collections;
using UnityEngine.EventSystems;

public class TouchExample : MonoBehaviour
{
    void Update()
    {
        // Check if there is a touch
        if (Input.touchCount > 0 && Input.GetTouch(0).phase == TouchPhase.Began)
        {
            // Check if finger is over a UI element
            if (EventSystem.current.IsPointerOverGameObject(Input.GetTouch(0).fingerId))
            {
                Debug.Log("Touched the UI");
            }
        }
    }
}

Note that for touch, IsPointerOverGameObject should be used with OnMouseDown() or Input.GetMouseButtonDown(0) or Input.GetTouch(0).phase == TouchPhase.Began.