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Opera's handling of unknown address types/protocols

If you attempt to open an address using a protocol which is not recognized or supported by Opera, you will see the following error message:

The address type is unknown or unsupported

Even though Opera cannot handle this protocol itself, it is possible to tell Opera to pass the URL on to the program that is set to be the default application for this protocol on your system.

In Opera, go to Tools > Preferences > Advanced > Programs and click the "Add" button under "Choose helper applications for other protocols". This will open a dialog box called "Protocols". Now, simply enter the protocol in the "Protocol" field without a colon or slashes (for example, you can enter "mms", but not "mms:" or "mms://"), and either set Opera to use the system default application to handle this protocol, or specify one in the "Open with other application" field.

Opera for Unix supports a set of parameters which can be used with trusted applications. These parameters are not supported on other platforms.

In Opera 7.11 and older, this requires editing the file Opera6.ini. To find the location of this file, go to the Help > About Opera menu and look for the "Preferences" path which points to this file.

Exit Opera and open Opera6.ini in a text editor. Under "[User Prefs]", add the following line

TrustedExternalURLProtocols=protocol

where protocol is the protocol in question, for example irc (IRC), rtsp (streaming media) or ed2k (eDonkey 2000).

It is possible to define several protocols by separating them with a comma, like this example:

TrustedExternalURLProtocols=irc,rtsp,mms,ed2k

Note! Please bear in mind that allowing Opera to automatically pass on unknown protocols like this could be a potential security problem, and it is done at your own risk. Any automatic handling of unknown data may pass it on to an application which might have a security flaw.