CPU spikes when typing in classic Outlook for Windows

Last Updated: April 24, 2025

ISSUE

When you write an email in classic Outlook for Windows, you may notice the CPU spikes up to 30 to 50% at some times and increases the power consumption. You can observe this if Task Manager is open while you type.

This issue can occur after updating to Version 2406 Build 17726.20126+ on Current Channel, Monthly Enterprise Channel, or the Insider channels.

STATUS: FIXED

The Word Team implemented a fix which will go to the following channels soon:

Beta Channel (Version 2505 Build 18822.15000) – ETA early May 2025, to check for build, go to Update History for Office Beta Channel - Office release notes. Current Channel Preview (Version 2505 18827.20000) – ETA mid May 2025, to check for build, go to Update History for Office Current Channel (Preview) - Office release notes. Current Channel (Version 2505 18827.20000) – ETA late May 2025, to check for build, go to Update history for Microsoft 365 Apps (listed by date) - Office release notes.

We found that the issue now occurs in Semi Annual Channel. If you urgently need to work around the issue the only option would be to revert to Version 2405. This is not recommended since there have been security updates since that version. To make the change do the following:

Locate the build of Version 2405 for the respective channel you are on from Update history for Microsoft 365 Apps (listed by date) - Office release notes.
Open a Command Prompt (Run as Administrator).
Type or past the command below and put the build from Step 1 and then press Enter:"%programfiles%\Common Files\Microsoft Shared\ClickToRun\officec2rclient.exe" /update user updatetoversion=16.0.17628.20144

Alternately you can use the Office Deployment Tool to switch to an earlier version of a channel. For more information, go to How to revert to an earlier version of Office.