How do I increase the speed of my IMAC?

Will increasing the memory increase the speed?

Increasing the RAM:

a) will not make a detectable difference in performance, and

b) is not economically feasible for that model because most people need professional help to access the buried RAM slots on that sealed-case model. Accessing the RAM slots requires an almost complete gutting of the computer. Some Apple Authorized Service Providers will not attempt the work.

You could spend piles of money on more RAM and the costly labor charges to install it, and not see one iota of improvement.

The most common cause of slow 21.5-inch iMacs made between 2012 and 2019 reported here is the slow factory hard drives Apple used† They are demonstrably slower than the base storage in 2011 iMac 21.5-inch models††. That is why the others asked for the information they did—to see what storage option your iMac came with.

If you up-ordered to the Apple Fusion drive or Apple's factory SSD and they are healthy, your computer should not feel slow. The reports requested may shed iight on the condition of your storage. Etrecheck will measure drive access speed and show if you have possible software conflicts (anti-virus; so-called "cleaning" apps; client-side VPNs; etc).

† — 2.5-inch laptop-class 5400rpm SATA 3GB

†† — 3.5-inch desktop-class 7200rpm SATA 3GB

You can use Activity Monitor to check if lack of memory is the culprit.

Run Activity Monitor, with the Memory tab open, while doing the things that cause the Mac to seem "slow". Watch the Memory Pressure graph (color-coded green/yellow/red) and the Swap Used:. A lot of yellows or reds, or a high Swap Used:, may be signs that insufficient RAM is causing a slowdown. If the graph is green and Swap Used: isn't very high, that indicates that you have enough RAM for what you are trying to do.

Just to add, posting the free EtreCheck report using the Additional Text option when posting will help to identify files that are launching on startup that may be slowing your computer down. It will also show the Read/Write speed of your Hard Drive that may point to a problem.

Using EtreCheck - Apple Community

Hey there!

If you find your Mac is running slowly, there are a number of potential causes that you can check first.

To start, let us know what exact model your Mac is and what version of macOS you’re using. The simplest way to find out is About This Mac, available by choosing About This Mac from the Apple menu  in the upper-left corner of your screen. 

Next, share a screenshot of your Mac’s storage information. In the Finder, choose Go > Utilities, then double-click the Disk Utility icon. (Disk Utility is located in the /Applications/Utilities folder.) Alternatively, click Launchpad in the Dock, type Disk Utility in the search field, then click the Disk Utility icon. Once Disk Utility is open, take a screenshot of the information it automatically opens to, which will be your startup disk. Next, select View > Show All Devices in Disk Utility and select the non-indented disk entry—it’s at the top of the hierarchy. Then, take a screenshot of the newly selected entry. Upload all screenshots here. 

Next, use Apple Diagnostics to test your Mac to help determine if there might be a hardware component at fault. When testing is complete, Apple Diagnostics shows the results, including one or more reference codes.

Learn about Apple Diagnostics reference codes

Let us know which reference codes you receive.

Finally, let us know what antivirus, VPN, or cleaning software you have installed. 

-Jack

If that iMac has a 1 TB Fusion Drive, that may not be a huge improvement over a 1 TB mechanical hard drive.

In 2017 iMacs, 1 TB Fusion Drives included a skimpy 32 GB of fast SSD storage – much less than the 128 GB that Apple shipped with 1 TB Fusion Drives before Late 2015.

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