Large Windows updates do a lot more than patching bugs and adding features; they (sometimes) reconfigure system files, unpack and install components, update drivers, and trigger post-update tasks. The resources used by these tasks and processes can often add up and slow down your PC temporarily, and are often the major cause of slowdowns after updates. The effect is more commonly felt by users with older hardware or specific configurations, though bad or buggy updates can affect a large variety of systems. There's usually no major cause for concern, though; most issues with a slower PC after a Windows update can be fixed at their source.

Background update tasks are running

Beep boop - finalizing update...

The Windows Module Installer (TiWorker.exe) is the main culprit in this case. It finalizes updates, including system patches, cumulative updates, optional features, and fixes. Windows triggers post-update cleanup and maintenance, which includes removing superseded update files, reorganizing system components, updating internal databases, and optimizing updated system files. The PC may also run general maintenance tasks after an update, such as disk checks, background indexing, and scheduled maintenance.

If you see TiWorker.exe/Windows Module Installer Worker consuming CPU and disk in the Task Manager, the best thing to do is wait a few hours. If the issue persists, check for pending updates and see if any additional packages are queued for installation (and install them if so). Running Windows Update troubleshoot or restarting can fix the updates if they're stuck.

Old or incompatible drivers

Updates can introduce changes to how hardware interfaces are handled

If your current drivers (especially graphics or chipset) are outdated or designed for older Windows versions, they might not work as well (or at all). The driver version delivered via Windows Update prioritizes broad compatibility and stability. That means generic or older drivers may remain even after an OS update, lacking the performance improvements or bug fixes provided by hardware vendors. Windows Update can also install a “basic” driver at times instead of the full-featured manufacturer-provided driver. This can cause buggy or slower performance than before the update.

The symptoms of outdated drivers can range from slow loading/boot times to general lag in everyday tasks and lower FPS in games (if graphics drivers are involved). Conflicting or corrupted drivers can also cause PC crashes. In such cases, it's best to roll back to previous versions or update to newer versions of the drivers. For graphics and chipset drivers in particular, a clean uninstall and reinstall of drivers can be helpful.

Windows Search Indexing

It can amp up after a major update

The purpose of indexing is to create a database of file locations, so searching via the search bar or File Explorer is fast. Creating or updating this index involves scanning files, reading metadata, writing index data to disk, and possibly parsing file contents. (Re-)indexing can occur after a significant update due to the changed or new files, and it uses CPU and disk resources. If Microsoft Outlook is updated, its index may be rebuilt (the time taken depends on your mailbox size). Meanwhile, if the index is corrupted during the update (worst-case scenario), it must be rebuilt from scratch, which can take hours to days. The slowdown from indexing is most likely to be noticeable on hard disk drives, slow low-power CPUs, and on PCs with inadequate memory (8GB or less).

If you find SearchIndexer.exe or SearchHost.exe running in Task Manager after an update, the indexer is working. Ideally, you should let it finish its job, which shouldn't take more than a few hours.

Re-enabled and reset bloatware and features

Windows can be sneaky sometimes

Milestone Windows updates (like shifting from 22H2 to 23H2) or version upgrades (from Windows 10 to 11) can behave like an OS reinstallation. This is because it replaces core system files and, in the process, often reinstates its default configuration files for the user interface and system behavior. This is not a bug, but a designed behavior to ensure new features are enabled, and the system is configured to a known, stable state. However, this overwrites many user-defined customizations. This often means resetting certain performance and privacy-related settings you had set. Background processes, visual effects, and pre-installed applications can reemerge due to this, consuming CPU, memory, and disk I/O, which becomes especially problematic when indexing takes place simultaneously.

If you have disabled visual effects for performance, recheck the menu in Advanced System Settings. For bloatware, look for apps in the Task Manager's "startup tab" for any apps you don't need/recognize, and disable them. You can also head over to the Installed Apps menu and uninstall any “free” or promotional apps you don't need.

A problematic update

Not an unfamiliar scenario

Cumulative Windows updates are complex as they integrate security patches, bug fixes, and new features for a wide variety of hardware and software configurations. Sometimes things can go wrong, with updates causing performance issues due to memory leaks, driver conflicts with specific hardware, or misconfigured power profiles. One of the most recent examples of this is the KB500… cumulative updates, which were linked to performance issues.

Microsoft has a "Windows release health" dashboard that documents known issues for each update; you'll find performance and stability problems listed there. To work around a faulty update, you can roll it back after confirming it is indeed the cause of the slowdown by checking with this database.

Windows Update slowdowns are usually temporary and nothing to worry about

A slow PC can be annoying, but slowdowns after a Windows update are mostly due to routine work and don't take long. In most cases, you might find your PC sluggish for a few minutes to hours, which you'll have to put up with. You should also check for the latest drivers manually and recheck important settings you had changed. In other, rarer cases, though, driver issues, bad updates, and new features/bloatware can be the cause; these should be tracked down and fixed, or they'll keep terrorizing your computer.