Note: this is a follow up bug for Bug 494092. Reproducible all the way back to Firefox 4.0, across platforms. STR: 1. Launch Firefox with a clean profile. 2. Access about:config and set the following pref to true: network.dns.disableIPv6 3. Restart the browser to make sure the change is applied. 4. Type in the following IPv6 URL: http://[FE80::0202:B3FF:FE1E:8329]/ ER: Since Bug 494092 landed and with 'network.dns.disableIPv6' set to true, any IPv6 URL should be considered a search string and a <default_engine> search should be performed for it. AR: Despite having 'network.dns.disableIPv6' set to true, Firefox is treating IPv6 URLs as URLs and attempts to access them. Additional notes: - This issue *is not a regression*. - This issue is reproducible across platforms. - See Bug 494092 Comment 36 for context, I believe it's reasonable to consider this bug a potential enhancement.

"network.dns.disableIPv6" Did you notice the "dns" part of the pref ? Setting this pref to true disables only the DNS resolution of names to IPv6 addresses. (example: mozilla.org -> [2620:101:8008:5::2:1] ) IPv6 URLs can be still accessed and that is what i would expect. There is no pref to disable IPv6 completely in Firefox/Gecko but that is what you are looking for.

i forgot to mark this report invalid...