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How to Install macOS on an External SSD to Speed Up Your Old Mac: 10 Easy Steps

Install macOS on an External SSD

In this article, we will learn How to Install macOS on an External SSD to Speed Up Your Old Mac (iMac, Mac mini, etc.). For this tutorial, I am using macOS Ventura.

Over time, numerous users of outdated iMac all-in-one PCs (Mac mini, etc.) have observed a considerable system slowdown, even while using standard applications. The most cost-effective and straightforward solution to this issue is to migrate and install macOS on an external SSD.

If you don’t want this hustle and still want to speed up your MAC, here are some guides you can use:
How to Speed Up macOS Catalina? 7 Easy Methods
How to Speed Up macOS Big Sur? 7 Easy Methods

How much faster can your Mac run?

After you have installed macOS on an external SSD, the most significant boost is seen in processing time, even for simple tasks. It is reported by users after upgrading to newer OS versions. However, the launch of macOS Mojave or macOS Catalina may still take a few minutes, and computer cleanup procedures only marginally improve the situation.

After installing macOS Ventura on an external SSD, the same computer's speed increased by 4 times.

No need for expensive repairs or disassembling the computer and taking it to a service center. While some uncertified service centers offer complete HDD to SSD replacement services, the cost of such a procedure, including the drive itself and labor charges, often outweighs the method’s effectiveness. Moreover, we do not recommend opening the device’s body and performing the replacement yourself for obvious reasons.

The most practical and cost-effective option is to add an external SSD, which functions as the system drive, and the standard HDD is used for file storage. The task can be divided into three simple stages:

  1. Back up the old HDD (optional). It is possible to do without this procedure by installing and configuring a clean system on an external SSD. Since access to the old HDD with the clean macOS installed on the SSD is retained, data from the HDD can be easily copied to a new external drive.
  2. Install the latest macOS version on a USB-connected SSD drive.
  3. Transfer data from HDD to SSD (optional).

All you need is the SSD drive and some free time. When selecting an SSD drive, keep in mind that the USB connection limits the work speed to about 400 MB/s. Therefore, it does not make sense to purchase a drive with read/write speed characteristics of 900 MB/s or more for this purpose. Note that the typical read/write speed of the standard HDD drive on the iMac 2013 release is approximately 100 MB/s.

Where to buy a good external SSD?

Here are a few popular options:

SanDisk 1TB Extreme Portable SSD

SAMSUNG SSD T7 Portable External Solid State Drive 1TB

How to Install macOS on an External SSD

1. Connect the external SDD to your Mac using a USB cable.

2. Restart your Mac.

3. When you turn on your Mac (at the very beginning of the boot), press and hold the ⌘Cmd + R key combination on your keyboard.

4. The Mac should boot into Recovery Mode (the boot takes longer than usual). If the computer booted normally, repeat step 2 and step 3 again.

5. From the menu that appears, select Reinstall macOS Ventura and click Continue.

6. Click Continue again.

7. Accept the license agreement by clicking Accept.

8. Click the Show all disks” button.

9. Select the connected SSD. It is usually indicated by a yellow icon.

If you face: This disk does not use the GUID Partition Table (GPT) schema. In most cases, this happens with newer SSDs that do not use the GUID Partition Table (GPT) scheme required to install macOS.

See our detailed instructions to prepare your external SSD for macOS installation (installing the GUID partition table diagram and the APFS file system).

10. Click Install. The macOS installation process begins, and you can continue with the installation.

Congratulations! You have successfully installed macOS on an external SSD.


Adding an external SSD to your system will result in a 4-fold increase in drive speed, significantly improving system and application startup times. Here are some advantages and disadvantages of this method:


  1. Speed. Using an SSD instead of an HDD (when connected to USB), the read/write speed can increase up to 4 times.
  2. Economy. Adding an external SSD is cheaper than a full HDD replacement, and the old HDD can still be used as file storage.
  3. Reversibility. You can easily switch back to the system on the HDD at any time.
  4. Simplicity. Even beginners can follow the instructions above to connect an external SSD and install macOS without opening the computer.


  1. Placement. The only drawback is the need to securely place the external SSD on the table or computer case, for which you can use unique covers or protectors.

You can also read: Best Apps for Mac: Top Selection For 2023

I hope this guide on How to Install macOS on an External SSD to Speed Up Your Old Mac was easy. If you face any issues, please comment below.

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