The majority of the time, your Mac is running slow the resources of your system are being used up by either what you're doing or what's going on in the background. You can also do other things to help your system hardware run.
Force Quitting Applications
Click the magnifying glass at the top right of your screen or press ⌘ (command) + SPACE.
Search for Activity Monitor and open it by pressing enter or clicking the application.
In the Activity Monitor, you should look at two tabs: CPU and Memory.
If your CPU is at maximum load, your tasks will be delayed while it processes your previous or background actions. You can press where it says % CPU and sort by the highest usage processes. WindowServer is an operating system process which manages your open windows. You'll see this at the top if you have many open windows. Closing applications will reduce its usage. Alternatively, look for high % usage tasks and press the close icon at the top of the window to Force Quit the process.
When you use up your memory, it'll begin running the process directly from your disk. Your disk has far slower read and write than your memory does. You may find that applications are slow to load and react, and your Internet may seem slow because you have no memory free.
Like the CPU, you can click the memory usage column to sort by the heaviest process and press the close icon at the top of the window to Force Quit the process.
Storage Full
If your disk is full or close to full, you're not allowing room for your system to read and write cache files. These are critical to fast performance and save information for faster load based on your usage.
Click about this Mac > Storage > Manage
Following the recommendations is always helpful. Reducing unused files and emptying your bin. You can also press the categories on the left where the GB values are high and remove applications and files you may no longer need.
Additionally, for any files you want to keep, we recommend backing them up or offloading the cloud storage. For more, visit our extensive guide here.
External Factors
Your Macs' ability to cool itself is essential. There are sensors built in which have a maximum operating temperature they're willing to run at before limiting your computer's resources.
Ambient Temperature. If you're in a hot and stuffy room or sitting in direct sunlight on a hot summer's day, you're likely reducing the performance of your laptop. While it tries to cool itself through fans and passively through the chassis, you're cycling in warm air or heating the chassis from the sun.
Restricting airflow. Are you working from your bed? If your MacBook is on your duvet, the fans are trying to draw air through vents that are covered up. Without it being able to pull air in, it only cools itself passively through the chassis. Not only is it inefficient, but your warming the duvet around the laptop, keeping the warmth in.