Microsoft Teams running slow on lecture / seminar room PCs

Illustration: PC screen with people attending Teams meeting

There have been reports of Teams running slow on lecture and seminar room PCs.

We have identified the following possible fixes:

Clearing the Teams cache

We have found the issue is more prone to happen with a very large Teams cache. See instructions at the end of this message to clear the Teams cache.

Sometimes the improvement in speed when clearing the cache is temporary, as the cache gets created again and soon gets back to it’s previous large size.

Accessing Teams on the web

If clearing the Teams cache doesn’t permanently fix the slow Teams issue then we recommend accessing Teams on the web when in a lecture or seminar room. This works perfectly fine and doesn’t suffer the same slowness as it does not use a Teams cache.

The Teams cache is stored in a user’s personal storage area on when accessing Teams on lecture and seminar room PCs. In your office the Teams cache would be stored on the local PC. This explains why the problem may not occur on your office PC but does in lecture and seminar rooms, and also why the problem can follow staff around different lecture and seminar rooms.

Looking further into for possible reasons as to why Teams may be slow with large caches in lecture and seminar rooms, we noticed the processors were reaching a sustained high load, indicating they were struggling to cope with the work they were being asked to do. To ease that load we added extra processors to the cluster to see if this would improve the Teams performance issue.

How to clear Teams cache

Fully quit Microsoft Teams and ensure it’s not still running in the toolbar at the bottom right of Windows.

  1. Quit Microsoft Outlook.
  2. Press Windows key + R to bring up the ruin box and type %appdata%/Microsoft/Teams in the text box and press enter.
  3. Select everything in the folder.
  4. Delete everything.
  5. Open Teams and wait for it to download required files.

It is important to do this from a lecturer or seminar room PC as the Teams cache is redirected to a network location on those PCs. On a staff desktop the Teams cache is stored on the local drive, so clearing the Teams cache from a staff PC won’t affect how it runs in a lecture theatre.

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