Cloning a disk has many benefits and is an easy way to manage your storage.
Cloning or changing the partitions of a failing drive can make the case worse. If the files matter, first see how hard drive and external drive recovery works.
Cloning creates an exact copy of your entire disk, which is useful when you want to make a backup or move your data to another drive.
Better still, it copies your operating system installation with all its preferences, programs and settings intact.
Before you clone your disk, though, it’s important to understand how the process works.
In this article, we explain how cloning works and when it makes sense, and how to do it correctly on Windows and on a Mac.
What is disk cloning?
Cloning a disk means making an identical copy of the original drive, including the operating system and all the files the computer needs to start up and run properly.
Many people confuse cloning with backing up, but the two differ in an important way:
- A backup copies your files: whether it’s in the cloud or on an external drive, a file backup only stores copies of your files; it can’t be used to start the computer.
- A clone copies absolutely everything: a cloned disk is identical to the original, so you can boot from it and use it normally.
When should you clone a disk?
You can clone your disk to create a complete backup, to migrate to a new drive or to make a drive upgrade easier, as explained below.
Create a full backup
A clone helps you get back up and running after a malware attack that damages your files, your data or even the whole operating system.
For example, if your PC is hit by ransomware, your files are encrypted and become unusable, and the attackers demand a ransom to decrypt them.
If you have a clone that was kept disconnected from the computer, you can replace the infected disk with it and get back the system, programs and files as they were when you made the clone, without paying the ransom. A clone that stays connected can be encrypted along with everything else.
Migrating to a new disk
When you replace your computer’s disk, you don’t need to reinstall everything: clone the old disk to the new one, and you can then put the old disk in an external enclosure and keep it as a backup drive. If you’re moving to a different computer, the clone may need new drivers, so the manufacturer’s migration tools are often a better choice.
Drive upgrade
Finally, when you decide to replace your hard drive with an SSD, cloning lets you move everything to the new SSD.
How does disk cloning work?
A few basic preparations make sure the cloning goes smoothly. Here they are:
Get a second drive
You obviously need somewhere to put the copy of your current drive – this can be a second internal drive or an external drive.
Buying a new disk isn’t enough. You also need a way to connect both drives at the same time.
On a desktop you can usually install the new drive inside the computer; on a laptop, a USB-to-SATA adapter or a USB enclosure (NVMe for M.2 SSDs) does the job.
Check the drive capacity
Make sure the destination disk (the one you’re cloning to) is at least as large as the source drive (the current one). Some programs can clone to a smaller disk by shrinking the partitions, as long as the used space fits.
Download a cloning tool
On Windows, Macrium Reflect Free was for years the most popular free option, but Macrium discontinued it in 2024. Free alternatives include Clonezilla and the free migration tool from your SSD’s manufacturer (for example, Samsung Data Migration for Samsung SSDs). On macOS, SuperDuper! is an alternative.
There are also paid tools with more features, such as Paragon Drive Copy and EaseUS Disk Copy Professional. Their advanced features include incremental cloning, scheduling, more elaborate file backups and encryption.
For basic use, a free tool is usually enough.
Make sure the destination disk holds no data you need
Everything on the destination disk will be permanently overwritten by the contents of the source drive. If it contains anything important, copy it somewhere else before you start. You don’t need to format it first: the cloning program overwrites it anyway.
Tidy up your original disk
Uninstall programs you don’t need and delete temporary files and duplicates. Why clone gigabytes you don’t need?
How to clone a disk in Windows
Once everything is ready, follow these steps to clone your disk in Windows:
1. Download and install a reliable disk cloning tool
Windows doesn’t include a true cloning tool. It does have an older built-in feature called System Image Backup, which Microsoft no longer develops.
System Image Backup doesn’t clone partitions: it creates a backup of the system that can only be restored to a disk at least as large as the original. To clone a disk, you need a dedicated cloning program. The steps below are generic: the exact option names vary from one program to another.
Note the difference: a disk image saves the whole disk into a single file, while a clone copies it directly from one disk to another.
2. Select the drive to clone
Select the disk you want to copy (the source disk) and choose the program’s disk cloning option.
3. Choose the destination disk
In the next window, choose the destination disk – the one that will receive the copy.
Remember that this will erase all the data on the destination disk, so double-check which one you choose.
Any partitions on the destination disk will be replaced by those from the source disk; some programs ask you to confirm this step.
If you’re cloning to a larger drive, check whether the program resizes the partitions automatically. If it doesn’t, extend the main partition to use all the available space, either in the program itself (if it allows it) or afterwards in Windows Disk Management.
4. Start cloning
Some programs let you schedule the clone, which is useful if you want to make regular copies of your drive as a backup.
Review the options you’ve chosen, confirm to start cloning and wait for the process to finish.
5. Enter the UEFI/BIOS to check that the clone works
Finally, to make sure everything works, start your computer from the cloned disk.
To do this, enter the BIOS (Basic Input/Output System) or UEFI (Unified Extensible Firmware Interface) and set the computer to boot from the cloned disk instead of the original.
Keep in mind that the BIOS is the firmware setup of your PC – on newer PCs it has been replaced by UEFI.
On older PCs, you enter the BIOS by pressing a key (or key combination) while the computer is starting up.
It’s usually F2, F12, Esc or Delete – the key is often shown on screen during startup.
In the BIOS, open the “Boot Order” or “Boot” menu and set the cloned disk as the first boot device.
To enter the UEFI from Windows, open the Start menu (in the bottom-left corner of the taskbar).
Click the “Power” button, hold down “Shift” and click “Restart”.
The PC restarts into the advanced startup options. Go to “Troubleshoot > Advanced options > UEFI Firmware Settings” and click “Restart”.
In the UEFI, set the computer to boot from the cloned disk.
Disk cloning on a Mac
To clone a disk on a Mac, follow these steps:
1. Open Disk Utility
Go to “Applications > Utilities > Disk Utility”, or open Spotlight with “Command + Space” and search for Disk Utility. To clone the startup disk, start the Mac in macOS Recovery and open Disk Utility from there, because a disk can’t be restored while the system is running from it.
2. Select the destination disk and click Restore
In the Disk Utility toolbar, choose “View > Show All Devices”.
Then, in the sidebar on the left, select the drive that will receive the clone.
Remember: at this point you’re selecting the destination drive, not the original one you want to copy.
Then click “Restore”.
3. Choose the original disk from the drop-down menu
In the “Restore from” menu, select the original drive. Disk Utility warns you that all the data on the destination disk will be erased.
Check carefully that you’ve chosen the right source drive in the drop-down menu before clicking “Restore”.
4. Wait for the cloning to finish before clicking “Done”
A progress bar fills up as the cloning progresses.
Only click “Done” once it’s completely full and the process has finished.
5. Start the Mac from the new drive to check the clone
Finally, start your Mac from the cloned disk to test it. On recent versions of macOS, and especially on Macs with Apple silicon, a copy of the system disk may not be bootable; in that case, use Time Machine or a tool such as SuperDuper to keep a full backup.
How long does it take to clone a disk?
It depends on two main factors: the amount of data to clone and the transfer speed of the drives and the connection between them.
At 100 MB/s, for example, cloning a disk with 500 GB of data takes about 90 minutes.
At half that speed, the same amount of data takes twice as long – around 3 hours.
In short: a faster transfer speed shortens the process, while more data makes it longer.
If both disks are inside the same PC, connecting them directly to the motherboard makes cloning faster than using an external drive over USB.
Also bear in mind that many drives transfer data much more slowly than their advertised maximum, because those figures don’t reflect the sustained transfer that cloning requires.
What to do when cloning gets stuck or takes too long?
Cloning can run into trouble when the old disk has bad sectors. The process may pause for long periods, freeze at a certain point or stop altogether.
In that case, turn to a professional data recovery service. Data recovery labs such as Bot use professional hardware imagers that can copy disks with damaged sectors, bad blocks and other faults while putting as little strain on them as possible.
If you’re having trouble cloning your disk, don’t keep trying: every attempt puts more strain on a failing disk and can destroy it. The copy needs to be made by professionals so that the disk – and the data – aren’t lost for good.
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Conclusion
Cloning a disk creates an exact copy of the original that you can usually boot from.
It’s useful for making a complete backup of valuable data, migrating to a new disk or upgrading to a solid-state drive (SSD).
To clone your disk, download and install a cloning tool, select the source drive, choose the destination and, once the process is complete, enter the UEFI/BIOS to check that the clone boots.
On both Mac and Windows, cloning can take a long time, depending on the transfer speed and the amount of data.
Finally, remember that cloning can also cause data loss – for example, if you pick the wrong destination disk or try to clone a failing disk – especially if you don’t have a backup of your files.
In those cases, the safest way to recover your data is to turn to a specialized professional service, so that the disk isn’t damaged any further.
At Bot, we recover data from disks safely. We work in a Class 100 (ISO 5) cleanroom: a particle-controlled environment that protects the integrity of your disk.
In addition, we have more than two decades of experience and more than 200,000 cases, including failing and damaged drives.
