Diagnosing IE11 performance issues within virtual environments when using UI16



Modern websites are becoming more and more resource intensive, including ServiceNow as new features are incorporated to make your instance more interactive, visually pleasant, and feature rich.

With the addition of new features, the load put on the web browser and hardware used to access ServiceNow increases as a result. This issue can be exacerbated by a lack of JavaScript optimization in Internet Explorer 11 when compared to other browsers such as Google Chrome  and Mozilla Firefox, requiring more resources than alternate browsers.

Computers bought within the last five years should easily have enough power to overcome IE11's lack of JavaScript optimization. However, when running in a virtual environment where there are fewer resources available than in a native environment, this lack of JavaScript optimization can become quite apparent.

Some examples of virtual environments are:

  • Citrix XenServer
  • VMWare VDI
  • Microsoft Hyper-V

One way that performance issues present is a longer loading time of a form. The form initially appears to load relatively quickly, but that is the initial part that is generated by the server, traverses the network, and renders on your machine. However, after these first few steps, the form will "freeze" for a number of seconds before it becomes usable, caused by the JavaScript executing upon page load to add a lot of the features to the form such as the Activity Stream, Client Scripts, Record Watcher, and UI Policy.

On a well-resourced machine, this freeze is brief and will take only a few seconds at most. However, if you are using IE11 and your environment does not have the appropriate resources, this freeze time can incfrease and become very visible and obstructive to users.


All ServiceNow Releases using UI16


IE11, virtual environments like Citrix, VMware etc.


Performance issues that can be attributed to lack of resources in your virtual environment will present across multiple websites, not just ServiceNow. If users are reporting performance issues in IE11 and you're running inside a virtual environment, be sure to check thoroughly whether your users are having performance issues with any other websites.

Another way to test is to use a web browser benchmarking tool such as the following:

Best practice is to run these tests in the same browser with the same operating system version both inside and outside your virtual environment. Doing so enables you to determine how much of the performance drop across tests can be attributed to the virtual environment.


Some of the various paths forward to ensure that ServiceNow will run well in your virtual environment are:

  • Consult with the vendor of your virtual environment to enquire about best practices related to web performance and implement their suggestions. They might suggest things such as:
    • Increasing the memory available to users of the virtual environment
    • Increasing the number of CPUs installed
    • Installing a GPU in your server (if you don't have one already) to which the graphics processing can be offloaded
    • Switching to an alternate browser
  • Switch to a browser that requires less load on the hardware when running modern websites (for example, Google Chrome).
  • Switch users operating inside the virtual environment back to UI15, which requires less performance from the browser, and thus will operate better in a low-resourced environment.
  • Disable ServiceNow features that require heavy JavaScript processing such as live forms, tabbed forms, and delayed related list loading.
  • Investigate and resolve performance issues caused by slow Client Scripts or UI Policies, for example, replace any that might be making a synchronous XMLHttpRequest with an asynchronous XMLHttpRequest.