Screen.resolutions

Description

All fullscreen resolutions supported by the monitor (Read Only).

The returned resolutions are sorted by width, lower resolutions come first. Note that the array will always be empty on Android devices since the resolution is variable (within reason) and so there is no restricted set of resolutions to choose from.

using UnityEngine;
using System.Collections;

public class ExampleClass : MonoBehaviour {
    void Start() {
        Resolution[] resolutions = Screen.resolutions;
        foreach (Resolution res in resolutions) {
            print(res.width + "x" + res.height);
        }
        Screen.SetResolution(resolutions[0].width, resolutions[0].height, true);
    }
}

See Also: Resolution structure, SetResolution.