iMac slow after update MAC OS Ventura 13.7.7 (22H722)

If you have a rotating disk hard drive it could be failing. Another excellent tool besides Etrecheck Pro to determine the state of your Mac is DriveDX. Download the free version, run it and report the results.

By the way, have you installed and run any "cleaning", "optimizing", "speed-up", anti-virus or VPN apps on your Mac?

Stewpotfromwa wrote:

Since Update installed 7 August 2025 my imac has become galcially slow - rotating wheel for 20 minutes etc

Based upon the the limited technical information provided.

I would suggest following the previous advise by @BDAqua and use the suggested application

This is a Diagnostic Tool that makes no changes to the computer.

It makes a coherent and readable inventory of both the Hardware and Software used on the computer 

The application is free or paid for added features. 

The Report will Not Reveal Any Personal Information. 

Post back the Full Report - Share Report >> Copy , then  paste  >>>> using the Additional Text Icon  <<<<

It would go a long ways at finding out the cause if you could provide an etrecheck report…

https://etrecheck.com/en/index.html