Slow performance after upgrading OS X on an older Mac is often caused by inadequate memory. Although you can install the upgrade on a Mac with 2 GB of memory, experience has shown that at least 4 GB is needed for full performance. Select About This Mac from the Apple menu.

Will updating my Mac slow it down?

No. It does not. Sometimes there is a slight slowdown as new features are added but Apple then fine tunes the operating system and the speed comes back. There is one exception to that rule of thumb.

Why is my Mac so slow after updating?

Slow performance may mean you’re about to reach the storage limit on your Mac. Solution: Check your hard drive space by clicking the the Apple icon in the top-left corner and then selecting “About this Mac.” Next, toggle over to the “Storage” section and wait for it to calculate how much space you’re using.