User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:63.0) Gecko/20100101 Firefox/63.0 Steps to reproduce: Upgraded Firefox on Windows 10 was updated to version 63. Tried to browse as usual. Actual results: Very slow browsing, page loads. Proxy is set to "Use system proxy settings" Expected results: Faster or the same loading as with version 62. Never used a proxy on this home computer so not sure what the setting was in previous versions. But the slowness is solved by selecting "No proxy". Problem and solution posted by others on Reddit

Hello Reporter, If you're using PAC file in the system proxy, it might be bug 1495024, which is resolved in 64. Can you try firefox beta (64) or nightly (65) to see if it works for you?

No, as I mentioned, I do not use a proxy at all on this home computer. I do not know what the setting was in version 62, but in 63 it was set to "Use system proxy settings". This may be a new option for version 63. The correct option in my case, and for others as reported on Reddit, is "No proxy." This should be the default setting, in my opinion.

The "use system default" setting is the right one and it's the default in Firefox for a long time but it causes slowness in Firefox63 due to bug 1495024 Can you please check a nightly Firefox version as requested to confirm that bug 1495024 also fixed your slowness ?

I downloaded today's nightly and installed it, then set the proxy setting to "Use system proxy settings". Browsing seems to be stable and fast as it was. So it looks like the bug fix will fix the issue I am having in the production version.

Thank you very much that you have tested the nightly ! I will mark this report as dupe of bug 1495024.