How to speed up a Mac using an external SSD


Unfortunately, sooner or later all computers begin to slow down. This also applies to the Mac – despite all the claims for better macOS optimization compared to Windows. There are certain measures you can take to speed up Apple's slow-down computer. For example, remove unnecessary programs, clear the system cache, disable Spotlight.

But all these tricks will be ineffective if you are the owner of an old Mac with an internal HDD.

Hard drives are noticeably slower than modern solid state drives. This is especially striking on new versions of operating systems. So, my iMac with OS X Mavericks in 2014 functioned very smartly, but after updating to El Capitan or Mojave, the system became incredibly inhibited.


A clean reinstall of macOS from scratch did not help, and working with a computer became decidedly impossible. Even the unfortunate TextEdit opened with a delay. In the meantime, some Photoshop started up, you could have time to tidy up the room.

The obvious solution is to migrate the system to an SSD. But there is one obstacle: installing an SSD in an iMac case is a tricky task, because not everyone can disassemble this device by unfastening the screen. I don’t want to take iMac to the service center either: they install SSDs only at unauthorized service points, they have less trust, and the price of this procedure, frankly, bites.

But there is an alternative – to connect an external SSD to the Mac via a USB cable. True, this solution is more suitable for owners of iMac monoblocks than for owners of MacBook laptops.


What do you need

Judging by the information provided by Apple, the data transfer speed through USB 3 and USB 3.1 of the first generation in the iMac can reach 5 Gb / s. And this is enough to connect an SSD ‑ drive as a system one. In principle, the iMac has a couple more Thunderbolt 2 connectors with the declared speed of up to 20 Gb / s. But SSD adapters for them are rare on sale and cost more, so we'll get by with a simple USB 3 port.

You will need an SSD ‑ drive, a case for it, and a USB ‑ cable.

You can read about how to choose an SSD in our guide. Just keep in mind that you don’t have to chase an expensive and wildly fast drive: anyway, the USB port will be a bottleneck preventing it from reaching its potential. Therefore, it is better to save a little: anyway, even a budget SSD will work much faster than your hard drive.

A particularly capacious drive is also not needed: it will house the operating system and programs, and all documents, photos and videos will be sent to the freed up HDD. So you can limit yourself to a 120 GB or less disk.

In my case, the system with applications and settings took up only 22 GB of disk space. If you plan to install heavy programs, for example for working with graphics and video editing, you will need a little more space.


I purchased a Samsung 860 EVO SSD with 250 GB and a silver case from Transcend, but you can choose any other accessories to your preference. If you still have the old SSD after the upgrade, then it will do. It will only be necessary to purchase a SATA-USB adapter, for example, such.

How to reinstall the system

Back up all documents, files, images, videos, and other good things that have accumulated on your Mac. To do this, you can use the built-in Time Machine tool or copy the necessary folders manually.

You will need another external drive because the Mac's built-in HDD and your new SSD must be formatted.

Install the SSD into the chassis, then plug it into the Mac via the supplied USB cable. Open Disk Utility and format your SSD in APFS format, if available, or in Mac OS Extended (Journal) with GUID Partitioning (on older versions of macOS).

            How to speed up a Mac using an external SSD

Now restart your Mac. Immediately after completing the process, press and hold Command + R. The macOS Utilities menu appears. Select Reinstall macOS.

            How to speed up a Mac using an external SSD

Click Continue, then accept the terms of the license agreement. You will be prompted to select a drive to install macOS. Specify your new SSD – it is highlighted in yellow. Click Install.

            How to speed up a Mac using an external SSD

Installation will take some time. When it is completed, the computer will restart. But, most likely, it will happen that you see the loading of your slow old system. That's because the Mac does not yet know that now you need to use SSD as the main disk.

Therefore interrupt the process and turn off the computer. Then activate the device again and hold down the Option key. Wait for the download manager window to appear.

            How to speed up a Mac using an external SSD

You will face two of your disks with macOS systems installed: the old and the new. The latter will be yellowish. Press and hold the Control key, then click the SSD drive – now the default download will always be from it. In the picture above, there is only one disk, because I already formatted the old HDD.

Wait until your new operating system boots up (you will not have to wait so long with an SSD). Now you need to remove the old one in order to free the built-in hard disk for the data. To do this, open the “Disk Utility” again, select the HDD there, left-click on it and click “Erase”. Specify APFS format and confirm erase. Done, you now have an extra hard drive for data.

How to transfer user profile

Finally, you can transfer your home folder to the free hard drive – this is an optional step. But if you want all your personal documents and files to be automatically saved on the HDD, it’s worth it.

Open System Preferences → Users and Groups. Click on the lock and enter your password. Now right-click on your username in the left panel and click on “Advanced Options”.

            How to speed up a Mac using an external SSD

In the "User folder" field, click "Select", create a new folder on the HDD with your name (without the Cyrillic alphabet), specify it and click OK. Then log out and log back in and your folders will be migrated.

Perhaps as a result of these manipulations, the names of your folders will change to English. To fix this, open "Terminal" and enter the command:

cd ~ / Documents; touch .localized

Documents will change back to “Documents”. In the same way, you can correct the names of Downloads to "Downloads", Music to "Music" and so on. This completes the reinstallation.

I reanimated my old iMac of 2014 in this way, and the effect of the SSD exceeded all expectations. Now the system boots in 30 seconds – on an old HDD, the waiting time could be 5 minutes or even 10 minutes. All applications – and even heavy Photoshop – also start without delay. So, if you do not want to take the Mac to a makeshift service or install an SSD on your own, external storage is an excellent compromise.

Read also

How to make a bootable USB flash drive with macOS

How to breathe new life into an old computer
                            What to do if the browser slows down


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