Our customers started reporting slow page load times issues with our site recently. We have yet to find a solid connection between any recent code changes on our site to performance issues. In fact, UI wise, things have remained the same for the pages in question.

What we've tracked it down to so far is that customers experiencing the slowness have Windows 8 with IE 11. If any of those customers try a Windows 10 machine with IE 11 on the same pages, load time increases dramatically. We're talking about the difference between 20 seconds on Win8/IE11 and 6 seconds on Win10/IE11.

From what we can tell, both machines are the same in terms of what network they are on, IE settings of concern match up (no proxy, always check for new content, do not delete cache on browser exit, smartscreen filter turned on).

Any ideas on what might be the difference or where else to look?

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  • There are online tools that make testing and benchmarking your site yourself with practically any configuration possible. So what do those benchmarks indicate? – Ramhound Oct 4 '17 at 23:11
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    Use Windows Performance Analyzer to find where the performance issue's occurring (see superuser.com/questions/1179273/why-is-ie-using-up-so-much-cpu/…). We had something similar this week, and traced it to a SEP (Symantec) definition update. – JohnLBevan Oct 5 '17 at 9:21
  • @Ramhound yes, that is the next step. Searching and asking questions first because pages that are slow are behind a login, so it is going to take some work to get that setup. I am not against that course of action. – slolife Oct 5 '17 at 22:21
  • There is a IE11 Windows 10 issue that was solved in the latest 1703 cumulative patch released last Tuesday. Proper benchmarking would have narrowed it down to a 1703 issue more then likely. here – Ramhound Oct 5 '17 at 22:27
  • Interesting about the 1703 cumulative patch. However, Win10 did not and does not experience the issue. But we did uninstall all of the Sept 2017 patches from the Win8 machine and performance returned to normal in IE11. – slolife Oct 6 '17 at 19:52

For now the answer is that we uninstalled the Sept 2017 windows patches from the Win8 machine and performance returned to expected levels. We haven't narrowed down which patch/KB it was yet. When we reinstalled all of the Sept patches, the performance dropped and the problem returned.


After opening a support ticket with Microsoft, they directed us first to install the October 2017 patches, which solved the problem. They also recommended that we try the following on a machine that just had the Sept 2017 patches:

Uncheck the two "Disable script debugging" options in Internet Explorer Advanced options tab.

We were able to see the performance issue disappear when those two options where unchecked, and the performance problems return when the options were checked.

I was not able to get precise information from Microsoft support about the exact issue/problem/bug that was causing this, but I also didn't have the time to dig in with them further, so I closed the ticket.

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  • FYI: The October 2017 patches are now available... it may be worth testing against in case that resolves the issues introduced by the September patch? – JohnLBevan Oct 23 '17 at 14:57

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