While Microsoft isn't changing the underlying browser add-on technologies in Internet Explorer 9, and is in fact retaining the old Manage Add-ons UI as well, the software giant is making one important change in this area. And as is the case with so much else in IE 9, the change will directly impact the performance of the browser. It's called the Add-on Performance Advisor, and while a system for automatically disabling unwanted add-ons during IE 9's initial setup may be preferable, this new UI does provide a handy UI for helping users decide which add-ons to disable.

If you're not familiar with it, Internet Explorer 8 included a hidden UI of sorts for finding out how long it took for individual browser add-ons to load. It was (and, in IE 9, still is) found in the Manage Add-ons interface, where a Load time column lets you sort add-ons by load speed.

IE 9 Add-on Performance Advisor

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That's all well and good, and in IE's case, the more add-ons you have installed and enabled, the slower the browser gets. But because this UI was essentially hidden--that is, you had to know it was there and where to find it--few users took advantage of this functionality. So in IE 9, a new Add-on Performance Advisor notification will pop-up automatically when you launch the browser and one or more add-ons exceeds a pre-set performance threshold.

This threshold, by default, is 0.2 seconds. And the notification, as you might expect, appears in the new IE 9 Notification Bar.

IE 9 Add-on Performance Advisor

If you click the Disable add-ons button, the following UI, new to IE 9, appears. This displays the add-ons, listed in reverse order by performance, and gives you a simple interface for disabling the worst offenders.

IE 9 Add-on Performance Advisor

You can also change the performance threshold if this interface pops up too frequently and you want slow but useful add-ons (like Last Pass) to run, regardless of the performance hit.

Secret: If you set the threshold above .2 seconds (mine is set to 1 second), the Add-on Performance Advisor notification may not appear again, and there's no other obvious way to access this interface from the IE 9 UI. To re-enable it, open the Registry Editor (regedit.exe) and navigate to Computer - HKEY_CURRENT_USER - Software - Microsoft - Internet Explorer - MAO Settings. Then, in the right pane, double-click the AddonLoadTimeThreshold value. In the Edit DWORD (32-bit) Value window that appears, change Base to Decimal and then change the Value date to 200. (This will return the threshold to its default .2 second value.) You will have to reboot for the change to take effect.