Content-length works for some file type and in different OS?


I want to get the length of my some type of file from my server like .mp4, .xml, .png, and custom file type .500!

I printed length with C# code in unity with :

public class Tmp_ContentLength : MonoBehaviour {
    public List<string> urls = new List<string> ();

    void Start () {

        for (int i = 0; i < urls.Count; i++) {
            print (urls*);*

StartCoroutine (GetFileSize (urls*,*
(size) => {
print ("File Size::> " + size);


IEnumerator GetFileSize (string url, Action result) {
UnityWebRequest uwr = UnityWebRequest.Head (url);
yield return uwr.SendWebRequest ();
string size = uwr.GetResponseHeader (“Content-Length”);

if (uwr.isNetworkError || uwr.isHttpError) {
print("Error While Getting Length: " + uwr.error);
if (result != null)
result (-1);
} else {
if (result != null)
result (Convert.ToInt32 (size));
URLs field fill with true Urls in the inspector.
So, I can get the length of all files in unity editor, but when I export .apk and run it, I will get print of .mp4 and .png, not .xml, and .500(my custom file type ).
1- Is there any issue or I,m wrong? 2- How can I enable Content-length header for .xml and my custom file type? 3- What is different between unity editor and android for getting Content-length?
Best Regards and sorry for bad English!

So, After try over and over! I found we need to disable gzip on sever and I do it with .htaccess files