Amended comments to MacKeeper tip
I initially wrote this comentary at the bottom of the tip:
Do not install MacKeeper - Apple Community
And given the tip itself is no longer editable, I am spinning off my commentary here.
Before doing any maintenance, it is important you backup your data. If you backup as a clone, and still have an optimizer, you will be able to remove the optimizer either by updating the backup, or booting off the backup and removing it with AppDelete, which is mentioned below.
MacKeeper and similar optimizers like Advanced Mac Cleaner have been frequent subjects that have come about in the forum. These programs run in the background and frequently delete essential cache files as they are written. The problem with this, is the cache files are used to help programs to launch, and other functions that optimize their speed. The assumption that deleting cache files speeds the Mac is only true if those files are seriously corrupt. Well guess what, if you delete it as it is being written, it can also get corrupted!
Instead of trying to use other software to optimize your speed, you need to be aware of the most common reasons for the Mac to slow down, and use tools to identify why the slow down is happening.
If you have already installed any of these optimizers, the quickest way to uninstall them is either through an uninstaller provided with them, or as long as the program is in the applications folder, its entire contents can be removed in Safe mode (holding the shift key on boot), with AppCleaner.
Use Devon Technologies EasyFind to locate all software with macpaw and zeobit to ensure you've captured the remaining files.
Once you have removed all optimizers, backup your data again, so the next restore doesn't restore the optimizer.
Both companies (Macpaw and Zeobit) created so-called optimizers such as MacKeeper, Advanced Mac Cleaner, and others which at best have a placebo effect on optimizing your system. If your Mac appears to be slow due to optimizer software, see this tip on reading and sharing Etrecheck results and the forum's frequent contributers can help you identify the cause.
Speed on the Mac is controled by:
Drive health - http://www.binaryfruit.com/ DriveDX and Apple's Disk Utility both can evaluate that without hurting the drive.
Drive being too full - 85% storage is an arbitrary point of diminishing returns where Macs have swap files constantly rewriting. Free up storage space - Apple Support
Background tasks such as iCloud syncing across slow upstream internet of large photo libraries, running Time Machine simultaneous to heavy disk activities, and other extensive background tasks. Apple menu -> System Settings/Preferences has a Time Machine panel that gives you control over putting Time Machine in the menubar and the option to tentatively turn on and off Time Machine. iCloud options to put your desktop and documents folders in the cloud should be done when you know you have the bandwidth upsteam on your internet to manage it. Most typical cable connections are 8 Mbps or less upstream, which is 1 MBps (B is Byte in uppercase, where b in lowrecase is bit). Meaning if you have a GB of data on your folder, it will take 1024 seconds to synchronize with the iCloud servers. Choose to backup what your bandwidth can manage automatically with what you do. Ask on the forum for advice if you need help planning.
Anti-virus software - Sophos, ClamAV, Malwarebytes, and Avast can all independently run a free scan manually without interfering with your regular operation. This other user tip goes into further detail how to fight it:
Effective defenses against malware and ot… - Apple Community
Don't run any anti-virus utility constantly as it may slow you down.
Don't run any firewall software. Leave that job to routers and WiFi base stations.
Optical drives - While not as frequently used, these are the slower than hard drives or solid state drives. When possible without breaking any copy protection rules, Disk Utility can make an image of an optical disk for faster access if you have sufficient storage on your hard disk. Some games though will not allow this, and you have to deal with the speed and cleanliness of your optical drive. Cleaning optical drives is not recommended with any liquids. There are special disks with brushes that clean the heads. Use of sticky labels and sharpies on to mark optical disks tend to slow if not make some discs unreadable. Jewelcases with inserts are the best way to physically catalog disks over using any marking or sticky labels.
Fusion drives are in fact combination solid state and platter hard drives frequently used on older Macs. Sometimes the data management on these drives can get split up. How to fix a split Fusion Drive - Apple Support explains how to fix that. An authorized service technician may be able to replace the fusion drive with a 100% solid state drive. Solid state can be up to 30 times faster than straight platter drives. Lack of use of solid state drives can shorten their life. As always to counter that, a good backup plan is necessary.
Hardware health. Use Apple Diagnostics to test your Mac - Apple Support
will help you determine if hardware that affects performance could have failed. It is an easier way, when it identifies an issue, to determine if you need to bring the machine in for service. If issues are reproducible with an erase and install from recovery (Intel, Apple Silicon), and no addition of any software or drivers, then you may also have a hardware issue. A negative result does not mean the hardware is 100% healthy, but a positive result does mean it needs service.
RAM can optimize multiprocessing. Most Macs these days have soldered RAM. An Authorized Service Technician can tell you if they can upgrade the RAM.