Department of Defense
High Performance Computing Modernization Program

Prior to 7.20b, Opera did not support IPv6. There is no way to disable IPv6 in Opera. To use Opera without IPv6, it is necessary to turn off IPv6 at the operating system level (which is typical browser behavior).

In versions earlier than 10.50 (for Microsoft Windows) or 10.63 (Apple OS X and Linux), Opera would always prefer IPv6 unconditionally over IPv4. This is especially a problem on current versions of Windows where IPv6 connectivity is enabled by default. The bug was fixed in March, 2010, when Opera started using the operating system's instead of their own built-in resolver library.

To be certain that the IPv6 protocol is being used to access a website, substitute an IPv6 literal address surrounded by square brackets in place of a domain name:



For additional information, refer to Request For Comments (RFC) 3986 “Uniform Resource Identifier (URI): Generic Syntax".

(Caution: This substitution can sometimes fail. Explanations of possible reasons for this are available. If you encounter problems, review the Broken User FAQ article found on that website for several possible explanations. For even more possible explanations, review this article on the ARIN IPv6 wiki.)