Version: 2017.2
public string error ;

Description

Returns an error message if there was an error during the download (Read Only).

If there was no error, error will return null or an empty string (this is because some platforms don't allow nulls for string values). We recommend that you use String.IsNullOrEmpty to check for the presence of an error so that both cases are covered.

If the object has not finished downloading the data, it will block until the download has finished. Use isDone or yield to see if the data is available.

using UnityEngine;
using System.Collections;

public class ExampleClass : MonoBehaviour { // Make a request with an invalid url public string url = "invalid_url"; IEnumerator Start() { WWW www = new WWW(url); yield return www; if (!string.IsNullOrEmpty(www.error)) Debug.Log(www.error); } }

In the example the URL is not valid so the error message will be "Couldn't resolve host".