Time Machine: What It Is, How It Works, How to Use It with Your Mac

Time Machine iconWhether you’re new to the Mac platform or have been using it for years, there’s one feature built into Mac OS X that you should not only know about, but use. That feature is Time Machine, a built-in backup application used to keep an up-to-date copy of all of the files on your Mac. Time Machine is unique among most backup applications in that it captures exactly what was on your Mac on any day in the past, making it easy to recover files, emails or media that may have been inadvertently deleted. While what Time Machine does is surprisingly complex, setting it up and using this feature is quite simple. We show you how to use Time Machine on your Mac:

Selecting a backup destination
To start setting up Time Machine, you need to have a backup destination — the device on which your files will be backed up. Time Machine can back up to many devices:

• An external hard drive or solid state drive connected to the Mac over USB, FireWire or Thunderbolt. OWC offers a huge variety of external drives, using FireWire, USB 2, USB 3, Thunderbolt and Thunderbolt 2 connections.

• An external hard drive or SSD connected to the USB port of an Apple AirPort Extreme 802.11ac or other Wi-Fi routers that specifically provide Time Machine compatibility over a Wi-Fi connection.

• An Apple AirPort Time Capsule or an OS X Server on the same network as your Mac.

How often does Time Machine back up your Mac, and for how long?
Time Machine performs a full backup of your Mac when it is first set up. This initial backup can take some time, so be patient and allow it to finish. Once the first backup is complete, Time Machine checks your Mac for new, changed, and deleted files once every hour. Time Machine keeps these hourly backups for the past 24 hours, then keeps a daily backup for the past month. It also keeps weekly backups for as long as the external drive that you’re using for Time Machine has available space. Once the backup drive is full, the oldest backups are deleted from Time Machine.

Related: Yes, You Can Use One Drive for Time Machine and File Storage

For this very reason, some Mac users prefer to use Time Machine for their regular backups, but make bootable full backups of their Macs frequently on another external drive using a backup utility like Carbon Copy Cloner or SuperDuper!.

Setting up Time Machine
With a properly-formatted and empty external drive, setting up Time Machine is simple — just connect it to your Mac. If this is the first time you’ve specified a backup device, Time Machine asks if you want to use that drive to back up the Mac with Time Machine:

Time Machine reacting to a new external drive

To use the drive as your backup disk, just click the “Use as Backup Disk” button and Time Machine begins the initial backup. That was easy, wasn’t it?

One thing you may want to do is encrypt your backup disk, so that it’s impossible for others to look at your backup files without knowing a password that you’ve set. This is also easy to set up; check the “Encrypt Backup Disk” box as seen in the image above, then provide a password when prompted.

The external disk you have purchased from OWC may or may not be formatted in the format that Time Machine needs. That format is called Mac OS X Extended (Journaled), which sounds daunting but really isn’t. If the drive isn’t in that format and is using the common Windows-based NTFS or FAT formats instead, Time Machine will prompt you to reformat the drive. Before you let it reformat the drive, realize that doing so completely erases all files on the external drive. If you’re thinking about re-using an older drive for Time Machine and wish to keep the files stored on it, then don’t reformat; get another drive that is blank.

Using Time Machine with an Apple AirPort Time Capsule
Apple’s AirPort Time Capsule is an interesting hybrid device, part backup external drive and part Wi-Fi router. The wireless capabilities are really useful with the MacBook line, as the laptops don’t need to be physically connected to a drive to stay backed up. The process of setting up Time Machine to work with an AirPort Time Capsule or other Network Attached Storage is different.

The AirPort Time Capsule needs to be set up properly and working prior to using it for Time Machine backups. Either a Mac or iOS device can be used to set up and configure the AirPort Time Capsule; full instructions for the setup process are included with the device, or can be downloaded here.

Once that’s done, click on System Preferences in the Dock on your Mac, then select Time Machine. The preference pane looks like this:

Time Machine preferences

Click the “Select Backup Disk” button, and something similar to the screen seen below appears:

Selecting Backup Disk in TIme Machine


The AirPort Time Capsule should appear as one of the Available Disks. If it doesn’t appear, click Other AirPort Time Capsule to select yours. Once you’ve selected the AirPort Time Capsule by highlighting it in the list with a click, click the “Use Disk” button. As before, you can select to encrypt your backup. There’s also a check box to “Show Time Machine in menu bar”. Some people may not want or care to know if Time Machine is in the middle of a backup, so if that’s the situation with you, just uncheck that box. If the Time Machine button Off/On button (see the image of the preference pane above) is in the Off position, click on it to turn Time Machine on. The backup begins.

The Initial Backup
Now comes the fun part; Time Machine backs up each and every file on your Mac. Fortunately, you can continue working on your Mac while it’s doing the backup. Be sure to leave your Mac on so that Time Machine is able to capture all of the information. Once the first backup is complete, you’ll see a notification similar to the one shown here:

Backup Complete

When using an AirPort Time Capsule, it’s sometimes much faster running the initial backup if you run an Ethernet cable between an Ethernet port on your Mac and an open Ethernet port on the AirPort Time Capsule.

Everyday Backups
After the initial backup is done, Time Machine automatically begins to back up any files that have changed on the Mac since the last backup, and it does this every hour on the hour as long as there’s a connection between the Mac and the backup destination. Even a MacBook set up with Power Nap (a function that allows the device to check for mail and other notifications on a regular basis while the MacBook is “sleeping”) will still perform Time Machine backups.

Provided that you didn’t uncheck the “Show Time Machine in menu bar” box described earlier, you’ll be able to see when a backup is taking place. Here’s what the Time Machine menu bar icon will look like under different conditions:

Time Machine is idle

This indicates that Time Machine is currently idle


Time Machine Backup In ProgressThe extra arrow in this icon indicates that Time Machine is working on a backup. On older versions of Time Machine, the arrow would move in a circle, which many Mac users found to be endlessly distracting.


Time Machine Alert Time Machine AlertIf you see either one of these icons, it means that something has happened that’s preventing Time Machine from backing up. Clicking on the Time Machine menu bar icon can show what’s causing the problem, or can just (as in the image below) display the current progress of a backup.

Time Machine Backup in progress


Let’s say you’ve just finished working on a very important document. To make sure that it’s safe from a possible drive failure on your Mac, you can manually start a Time Machine backup. From the Time Machine menu, select “Back Up Now” to start things up.

Back Up Now


On occasion, it’s good practice to verify the backup disk to make sure it is sound. Selecting this menu while pressing the Option key provides the option of verifying backups or even switching to a different backup disk.

Restoring files or versions of files from Time Machine Backups
The entire reason you use Time Machine to back up your Mac is to be able to retrieve accidentally deleted or corrupted files, or to restore an entire system if your primary (usually internal) storage fails. In this section, we’ll show you how to restore a file from a particular point in time. If you need information on how to restore an entire system, that’s later on in this article.

When looking for a file or folder on your Mac, switch to the Finder then choose “Enter Time Machine” from the Time Machine menu. Your Mac display transforms into something that looks like this:

Enter Time Machine

Image courtesy of Apple Inc.

On the right side of this window is a timeline showing various dates and times back until the oldest backup saved by Time Machine. To reach a specific point in time, click on the appropriate line on the timeline. If you’re not sure when you deleted or changed a file, use the up arrow located just to the right of the Finder window to travel “back in time”. When the folder or file you’re missing or that you changed appears, stop at that point in time.

Sometimes you know the name of the file that you’re looking for. You can search from the Time Machine Finder window by typing a search term into the Search field on the top right of the Finder window. Then use the up (back in time) arrow to have Time Machine search through the backups to find the file or folder.

To restore a file or folder, just select it by clicking on it, then click the “Restore” button seen below the Finder window. Unsure if it’s the right version of the file? Use Quick Look before you restore it by just pressing the space bar once you have selected the file.

When the file is restored, it’s actually copied to the Mac desktop or the folder that the file was originally in. Sometimes, you may be restoring an earlier version of a file with the same name as one that’s already in a folder — if that’s the case, you’ll be asked to select which of the two files to keep, or if you want to keep both. Right-clicking or control-clicking on a file in the Time Machine window display additional options.

Restoring or Reverting in Apps
Some apps — Pages being a perfect example — support a way to revert to earlier versions of documents while in the app. To do this, open a file that you want to revert to an earlier version of and then either select Enter Time Machine from the Time Machine menu, select File > Revert to > Browse All Versions from the menu bar (if this doesn’t exist, then the app doesn’t support Time Machine directly), or if you have a Time Machine icon in the Dock, click on it.

Every version of the document that has been saved appears on the screen in the now-familiar Time Machine timeline. Once you’ve found the version you wish to revert to, just click the Restore button underneath to copy it back to the present time.

Restoring a Mac From a Backup
One of the most depressing situations a Mac user can run into is having a primary storage device fail. But it doesn’t have to mean that you’re down and out! Once the drive has been replaced, it’s actually quite simple to restore the entire system from your Time Machine backup. Here’s what you do once there’s a new drive in your Mac:

1.) Connect the Mac and the Time Machine drive, and turn on the Time Machine drive. If the Time Machine drive is on the network — a AirPort Time Capsule, for example — make sure that the Mac is on the same network before proceeding.

2.) Either restart the Mac using Apple menu > Restart, or turn the Mac on if it’s currently shut down. Once the Mac boots and you hear the startup chime, hold down the Command (⌘) key and R key simultaneously. When the Apple logo appears on the screen, you can release the keys, and the Mac boots up from the Recovery partition stored on the drive and into OS X Utilities

3.) From the list of OS X Utilities, select “Restore From Time Machine Backup”, then click the Continue button.

4.) Next, select the Time Machine backup. If it’s on an external backup disk, select it by clicking on it, then click Continue. When the Time Machine backup is on an AirPort Time Capsule, select the network from the AirPort menu on the right side of the menu bar, select the Time Capsule, then click “Connect to Remote Disk”. Finally, if the Time Machine backup is stored on a network backup disk (for example, an external drive connected to a Wi-Fi router or an OS X server), select it, and then click “Connect to Remote Disk”

5.) You may be asked to enter a name and password to connect to the backup disk. If requested, enter the appropriate information, then click Connect.

6.) A list of the dates and times of backups appears. Select the one you want — usually the most recent — then follow the onscreen instructions to restore all data and settings onto your Mac.

Once the system has been restored, Time Machine will probably perform a full backup at the next scheduled backup time. This is perfectly normal, and the hourly backups begin again once the full back is done.

For a look at how one drive can be used for both Time Machine backups and for storing your files, please visit: http://blog.macsales.com/36128-yes-you-can-use-one-drive-for-time-machine-and-file-storage


  • My Time Machine (2 years old) has recently failed. My MacBook Pro does no longer recognizes it. Tests with other MacBooks have the same results. What are my options? Prorated replacement possible? How?

  • its a very much
    and scientifically posible at all

  • I agree about the need to call Unitrends support frequently. However they definitely make an effort to get things fixed fully.

  • Do multiple external drives need to have the same name

  • I have my MacPro & iMac backed up to Time Machine. It works great to find a lost file.

    BUT, when the 2 TB HD recently filled up, it stopped backing up & I was forced to Erase the HD & start over.

    I thought Time Machine would sequentially delete the oldest files once it filled up.

    Is there something I have done wrong?



    • Hello John,

      Thank you so much for your question. It is very possible that the amount of DATA from your MacPro and iMac have surpassed 2TBs of DATA. If you are trying to transfer more DATA then the Time Machine back up allows, you will see this problem!

      Please feel free to contact our Technical Support Team and we will be happy to look further into this with you!

      • Hi Dyllon,

        I have also experienced this issue. I was (also) under the impression from what I’ve read that OLD backups were deleted automatically to allow for new ones once the 2TB had be filled up. I’m using MacBook Pro, TimeMachine & my Apple external hard drive (the flat-ish & almost square one).

        For 94 days I couldn’t do a backup – so today I did some research – discovered I was missing the latest firmware update so got that sorted – & right now thebackup is finally underway but it says it’s up to 4MB out of 212MB & am using wireless modem with ASDL internet connection. It’s going ok though.

        Due to previous issues though (pre the firmware update today) I’m half expecting to get a message telling me there is no room for the backup!

        How do I manually get rid of old backups / data on my external drive??

        Hoping you can help me to finally sort out this annoying problem. Am not working so cannot afford to get a new device to back up to. If that’s the solution.

        Kind regards

  • In the part where it says (see below in quotation marks) select yours after selecting Other Airport Time Capsule I don’t get a Select Yours option. instead, after selecting Other Airport Time Capsule I get a “Set up” option but when I click on it, I am not able to set it up because there is no window to do that.
    I have been using my Airport Time Capsule as a router for a year but never did set it up as a back up. How do I get that “Set up ” now message.

    “The AirPort Time Capsule should appear as one of the Available Disks. If it doesn’t appear, click Other AirPort Time Capsule to select yours. Once you’ve selected the AirPort Time Capsule by highlighting it in the list with a click, click the “Use Disk” button. As before, you can select to encrypt your backup.”

  • Nice article.

    Something not shown is that Time Machine can also backup data on external drives connected to the Mac.

    For example, I have Time Machine back up all video and photo files, along with Adobe and Final Cut Pro libraries, on my external OWC Thunderbay 4 Raid5, and it does it just fine.

    Just click on OPTIONS on the Time Machine settings panel, and under “exclude these items from backup” click on one of your external drives shown, and then choose the minus-sign “-” at the bottom to take the external drive off of the list of items excluded from backup — and it will start backing it up!

    Then, if you don’t want some folders or files backed up, ADD them (with the plus-sign “+”) to the exclude list, using the full path name. Nice and easy!

  • Pretty thorough article but one thing folks should know is that Time Machine will eventually use all the available space on your drive. If you have are using the drive for other data, it is wise to partition the drive to limit Time Machine’s usage of space.

    You can use more than one drive for backups and Time Machine will alternate, backing up to one drive, then the next backup to the second drive.

    Also, someone correct me if I am in error here but when Time Machine deletes backups, it deletes the oldest files individually but will never delete the only copy of a file.

    • My experience with a 500 GB as a Time Machine did hit the full disk and the oldest files were eliminated. And that did include the only copy of a file. Precious information and memorabilia I now store in multiple places; SD/SDXC card, CD/DVD disk, 2nd external drive and iCloud. While I did have 3 computers on the same Time Machine and space was being swallowed up very fast, I have allocated an additional drive to act on only one computer daisy chained on firewire.

  • Excellent article. I finally understand how to use Time Machine backup system. Well done.