A slow Mac can be caused by many different issues. In this article, we'll take a look at some of the more common problems and their possible solutions.

1. The available system memory (RAM) is low:

The system memory or RAM is where any open applications and files are stored when they are in use. Too many simultaneously open programs and files can use up all the available memory and cause slow performance or sluggish behavior in software.

You can use the application Activity Monitor that comes with Mac OS to check the available memory and how much is being used:

Take a look at the "Memory Pressure" graph in the lower left, if the graph is green you have plenty of memory left, if it's yellow then you are close to running out, if it's red then you have used all of the available system memory.

2. A cluttered desktop:

A commonly overlooked culprit of slow performance is a desktop covered in many files, this can be even more of an issue when file preview is turned on. With file preview enabled, each file icon on your desktop is a small "mini-window" that the computer has to draw and render, which takes more resources to do.

There are two solutions, first, you can organize your files into folders and clean up the desktop. Alternatively, if you prefer to keep many files on the desktop, turning off the file preview function which may resolve the issue by decreasing the workload.

To disable file preview for the desktop:

1. Click anywhere on the desktop that is free of icons

2. From the top menu bar select view > show view option

3. Uncheck the box "Show icon preview" 

3. Out of date MacOS:

Updates to the MacOS Operating System can come with improvements that help keep your system performing at its best. It's always a good idea to stay updated to the latest version. To check what version you're running, use the following steps.

1. Click the Apple menu icon in the upper left of the toolbar and select "About this Mac"

2. From this screen, select the button "Software Update..."

3. From this Screen you'll see if a software update is available or if you are up to date:

4. Too much stuff:

Your Mac comes with some tools to help clear out the less obvious places and help manage your space. Follow these steps to find those tools:

1. Click the Apple menu icon in the upper left of the toolbar and select "About this Mac"

2. Click the "Storage" tab along the top and then the button "Manage..." you'll see the following screen:

From this page, you can use the tools on the right to help reduce used storage space which can help performance. Along the left side, you can see the major categories of what is using space on your Mac, this information can be useful in helping to determine where most of your space is allocated.

5. Startup Slowdown:

Too many items set to open when you're computer starts up can seriously slow you down, try to keep them to the minimum with these steps:

1. Click the Apple menu icon in the upper left of the toolbar and select "System Preferences..."

2. Select "Users & Groups"

3. Select "Login Items" on the right

Be sure to select the line with the application you want to remove and press the minus button at the bottom of the window to remove the application from starting when you start your Mac. You can also choose to hide the application after it starts on startup, keep in mind however that application will still use memory and resources when running hidden in the background. 

6. Clear the cache:

Applications can store data that is supposed to be temporary in your MacOS cache, although sometimes things don't always get deleted as they should and these files can accumulate over time. Here's the steps to clear out your cache:

1. Open Finder and then from the Go menu select "Go to Folder..."

2. Type "~/Library/Caches" and click Go, you'll see a list of folders:

3. Note: You should only perform this step if all applications are closed with any files you were working on saved. Expand each folder and delete the contents inside, but we recommend leaving the actual folder. 

7. Slow Internet

Since most apps today require an internet connection, you'll see a beachball when one of these apps cannot send or receive data because of a problem with your internet connection.  Examples include weak WiFi signals, intermittent internet connections, and too many other applications downloading too much data at the same time.