The file extensions .CRT and .CER are interchangeable. If your server requires that you use the .CER file extension, you can change the extension by following the steps below:
Using a Windows based computer
Double-click on the yourwebsite.crt file to open it into the certificate display.Select the Details tab, then select the Copy to file button. Hit Next on the Certificate Wizard. Select Base-64 encoded X.509 (.CER), then Next. Select Browse (to loca