How to Change Opera User Agent String

Method 1: Through Browser Menu

1. In Opera browser, click on Tools -> Quick Preferences -> Edit Site Preferences.
2. Go to Network tab.
3. Under the Browser Identification section, select appropriate option. 5 options are avaible:

   1: Identify as Opera
   2: Identify as Firefox
   3: Identify as Internet Explorer
   4: Mask as Firefox
   5: Mask as Internet Explorer 

4. Click OK when done.

Method 2: Through opera:config

1. Type opera:config into the Opera location address bar and hit Enter to open Preferences Editor.
2. Type Spoof UserAgent ID into the quick find box next to “Show All”.
3. The “Spoof UserAgent ID” setting will be shown. Change the value to a numerical value between 1 to 5 (both inclusive), which represents the following:

   1: Identify as Opera
   2: Identify as Firefox
   3: Identify as Internet Explorer
   4: Mask as Firefox
   5: Mask as Internet Explorer

4. Click on Save when done.

The only difference between “Identify as …” and “Mask as …” is the resulting User-Agent string sent to the servers. When Opera is set to identify as other browser, the term “Opera” and its version number are still present in the UA string. While, when a user sets Opera to mask as Firefox or IE, it completely hides itself from the UA string, and the standard UA string of that browser is sent to the web servers.