QualitySettings.vSyncCount

Description

The VSync Count.

The number of VSyncs that should pass between each frame. Use 'Don't Sync' (0) to not wait for VSync. Value must be 0, 1, 2, 3, or 4.

using UnityEngine;

public class Example : MonoBehaviour
{
    void Start()
    {
        // Sync framerate to monitors refresh rate
        QualitySettings.vSyncCount = 1;
    }
}

See Also: Quality Settings.