Choose your iMac model

If you're not sure which iMac you have, you can identify your iMac and then select it from the list below.

27-inch

24-inch

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21.5-inch

• iMac (Retina 4K, 21.5-inch, 2019)*
• iMac (Retina 4K, 21.5-inch, 2017)*
• iMac (21.5-inch, 2017)*
• iMac (21.5 inch, Mid 2014)*
• iMac (21.5-inch, Late 2013)*
• iMac (21.5-inch, Late 2012)*

20-inch

17-inch

* Memory is not removable by users on iMac (21.5-inch, Late 2012), iMac (21.5-inch, Late 2013), iMac (21.5-inch, Mid 2014), iMac (21.5-inch, 2017), iMac (Retina 4K, 21.5-inch, 2017), and iMac (Retina 4K, 21.5-inch, 2019). If the memory in one of these computers needs repair service, contact an Apple Retail Store or Apple Authorized Service Provider. If you’d like to upgrade the memory in one of these models, an Apple Authorized Service Provider can help. Before you schedule an appointment, confirm that the specific Apple Authorized Service Provider offers memory upgrade services.

Memory in iMac (21.5-inch, Late 2015), and iMac (Retina 4K, 21.5-inch, Late 2015) is not upgradeable.

iMac (Retina 5K, 27-inch, 2020)

Get memory specifications for iMac (Retina 5K, 27-inch, 2020), then learn how to install memory in this model.

Memory specifications

This iMac model features Synchronous Dynamic Random-Access Memory (SDRAM) slots on the rear of the computer near the vents with these memory specifications:

For optimal memory performance, DIMMs should be the same capacity, speed, and vendor. Use Small Outline Dual Inline Memory Modules (SO-DIMM) that meet all of these criteria:

• PC4-21333
• Unbuffered
• Nonparity
• 260-pin
• 2666MHz DDR4 SDRAM

If you have mixed capacity DIMMs, see the install memory section for installation recommendations.

iMac (Retina 5K, 27-inch, 2019)

Get memory specifications for iMac (Retina 5K, 27-inch, 2019), then learn how to install memory in this model.

Memory specifications

This iMac model features Synchronous Dynamic Random-Access Memory (SDRAM) slots on the rear of the computer near the vents with these memory specifications:

Use Small Outline Dual Inline Memory Modules (SO-DIMM) that meet all of these criteria:

• PC4-21333
• Unbuffered
• Nonparity
• 260-pin
• 2666MHz DDR4 SDRAM

iMac (Retina 5K, 27-inch, 2017)

Get memory specifications for iMac (Retina 5K, 27-inch, 2017), then learn how to install memory in this model.

Memory specifications

This iMac model features Synchronous Dynamic Random-Access Memory (SDRAM) slots on the rear of the computer near the vents with these memory specifications:

How Can I Free Up Memory On My Imac

Use Small Outline Dual Inline Memory Modules (SO-DIMM) that meet all of these criteria:

• PC4-2400 (19200)
• Unbuffered
• Nonparity
• 260-pin
• 2400MHz DDR4 SDRAM

iMac (Retina 5K, 27-inch, Late 2015)

Get memory specifications for iMac (Retina 5K, 27-inch, Late 2015), then learn how to install memory in this model.

Memory specifications

This iMac model features Synchronous Dynamic Random-Access Memory (SDRAM) slots on the rear of the computer near the vents with these memory specifications:

Use Small Outline Dual Inline Memory Modules (SO-DIMM) that meet all of these criteria:

• PC3-14900
• Unbuffered
• Nonparity
• 204-pin
• 1867MHz DDR3 SDRAM

For these 27-inch models

Get memory specifications for the following iMac models, then learn how to install memory in them:

• iMac (Retina 5K, 27-inch, Mid 2015)
• iMac (Retina 5K, 27-inch, Late 2014)
• iMac (27-inch, Late 2013)
• iMac (27-inch, Late 2012)

Memory specifications

These iMac models feature Synchronous Dynamic Random-Access Memory (SDRAM) slots on the rear of the computer near the vents with these memory specifications:

Use Small Outline Dual Inline Memory Modules (SO-DIMM) that meet all of these criteria:

• PC3-12800
• Unbuffered
• Nonparity
• 204-pin
• 1600MHz DDR3 SDRAM

Installing memory

The internal components of your iMac can be warm. If you've been using your iMac, wait ten minutes after shutting it down to let the internal components cool.

After you shut down your iMac and give it time to cool, follow these steps:

1. Disconnect the power cord and all other cables from your computer.
2. Place a soft, clean towel or cloth on the desk or other flat surface to prevent scratching the display.
3. Hold the sides of the computer and slowly lay the computer face-down on the towel or cloth.
4. Open the memory compartment door by pressing the small grey button located just above the AC power port:
5. The memory compartment door will open as the button is pushed in. Remove the compartment door and set it aside:
6. A diagram on the underside of the compartment door shows the memory cage levers and the orientation of the DIMM. Locate the two levers on the right and left sides of the memory cage. Push the two levers outward to release the memory cage:
7. After the memory cage is released, pull the memory cage levers toward you, allowing access to each DIMM slot.
8. Remove a DIMM by pulling the module straight up and out. Note the location of the notch on the bottom of the DIMM. When reinstalling DIMMs, the notch must be oriented correctly or the DIMM won't fully insert:
9. Replace or install a DIMM by setting it down into the slot and pressing firmly until you feel the DIMM click into the slot. When you insert a DIMM, make sure to align the notch on the DIMM to the DIMM slot. Find your model below for specific installation instructions and notch locations:
   • iMac (Retina 5K, 27-inch, 2020) DIMMs have a notch on the bottom, slightly left of the middle. If your DIMMs are mixed in capacity, minimize the capacity difference between Channel A (slots 1 and 2) and Channel B (slots 3 and 4) when possible.
     
   • iMac (Retina 5K, 27-inch, 2019) DIMMs have a notch on the bottom, slightly left of the middle:
   • iMac (27-inch, Late 2012) and iMac (Retina 5K, 27-inch, 2017) DIMMs have a notch on the bottom left:
     
   • iMac (27-inch, Late 2013) and iMac (Retina 5K, 27-inch, Late 2014, Mid 2015, and Late 2015) DIMMs have a notch on the bottom right:
     
10. After you install all of your DIMMs, push both memory cage levers back into the housing until they lock into place:
    
11. Replace the memory compartment door. You don't need to press the compartment door release button when replacing the compartment door.
12. Place the computer in its upright position. Reconnect the power cord and all other cables to the computer, then start up the computer.
    

Your iMac performs a memory initialization procedure when you first turn it on after upgrading memory or rearranging DIMMs. This process can take 30 seconds or more, and the display of your iMac remains dark until it's finished. Make sure to let the memory initialization complete.

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For these 27-inch and 21.5-inch models

Get memory specifications for the following iMac models, then learn how to install memory in them:

• iMac (27-inch, Mid 2011)
• iMac (21.5-inch, Mid 2011)
• iMac (27-inch, Mid 2010)
• iMac (21.5-inch, Mid 2010)
• iMac (27-inch, Late 2009)
• iMac (21.5-inch, Late 2009)

Memory specifications

Use Small Outline Dual Inline Memory Modules (SO-DIMM) that meet all of these criteria:

i5 and i7 Quad Core iMac computers come with both top memory slots populated. These computers will not start up if only a single DIMM is installed in any bottom slot; these computers should operate normally with a single DIMM installed in any top slot.

Core Duo iMac computers should operate normally with a single DIMM installed in any slot, top or bottom. ('Top' and 'bottom' slots refer to the orientation of the slots in the pictures below. 'Top' refers to the slots closest to the display; 'bottom' refers to the slots closest to the stand.)

Installing memory

The internal components of your iMac can be warm. If you've been using your iMac, wait ten minutes after shutting it down to let the internal components cool.

After you shut down your iMac and give it time to cool, follow these steps:

1. Disconnect the power cord and all other cables from your computer.
2. Place a soft, clean towel or cloth on the desk or other flat surface to prevent scratching the display.
3. Hold the sides of the computer and slowly lay the computer face-down on the towel or cloth.
4. Using a Philips screwdriver, remove the RAM access door in the bottom of your computer:
   
5. Remove the access door and set it aside.
6. Untuck the tab in the memory compartment. If you're replacing a memory module, gently pull the tab to eject any installed memory module:
   
7. Insert your new or replacement SO-DIMM into the empty slot, noting the orientation of the keyway of the SO-DIMM as shown below.
8. After you insert it, press the DIMM up into the slot. There should be a slight click when you seat the memory correctly:
   
9. Tuck the tabs above the memory DIMMs, and reinstall the memory access door:
   
10. Place the computer in its upright position. Reconnect the power cord and all other cables to the computer, then start up the computer.

For these 24-inch and 20-inch models

Get memory specifications for the following iMac models, then learn how to install memory in them:

• iMac (24-inch, Early 2009)
• iMac (20-inch, Early 2009)
• iMac (24-inch, Early 2008)
• iMac (20-inch, Early 2008)
• iMac (24-inch Mid 2007)
• iMac (20-inch, Mid 2007)

Memory specifications

These iMac computers have two side-by-side Synchronous Dynamic Random-Access Memory (SDRAM) slots in the bottom of the computer.

The maximum amount of random-access memory (RAM) you can install in each computer is:

You can use a 1GB or 2GB RAM module in each slot for iMac (Mid 2007) and iMac (Early 2008). Use 1GB, 2GB, or 4GB modules in each slot for the iMac (Early 2009).

Use Small Outline Dual Inline Memory Modules (SO-DIMM) that meet all of these criteria:

DIMMs with any of the following features aren't supported:

• Registers or buffers
• PLLs
• Error-correcting code (ECC)
• Parity
• Extended data out (EDO) RAM

Installing memory

The internal components of your iMac can be warm. If you've been using your iMac, wait ten minutes after shutting it down to let the internal components cool.

After your iMac cools down, follow these steps:

1. Disconnect the power cord and all other cables from your computer.
2. Place a soft, clean towel or cloth on the desk or other flat surface to prevent scratching the display.
3. Hold the sides of the computer and slowly lay the computer face-down on the towel or cloth.
4. Using a Philips screwdriver, remove the RAM access door in the bottom of the computer:
   
5. Remove the access door and set it aside.
6. Untuck the tab in the memory compartment. If you're replacing a memory module, untuck the tab and pull it to eject any installed memory module:
   
7. Insert your new or replacement RAM SO-DIMM into the empty slot, noting the orientation of the keyway of the SO-DIMM as shown above.
8. After you insert it, press the DIMM up into the slot. There should be a slight click when you seat the memory correctly.
9. Tuck the tabs above the memory DIMMs, and reinstall the memory access door:
   
10. Place the computer in its upright position. Reconnect the power cord and all other cables to the computer, then start up the computer.

For these 20-inch and 17-inch models

Get memory specifications for the following iMac models, then learn how to install memory in them:

• iMac (20-inch Late 2006)
• iMac (17-inch, Late 2006 CD)
• iMac (17-inch, Late 2006)
• iMac (17-inch, Mid 2006)
• iMac (20-inch, Early 2006)
• iMac (17-inch, Early 2006)

Memory specifications

For best performance, fill both memory slots, installing an equal memory module in each slot.
*iMac (Late 2006) uses a maximum of 3 GB of RAM.

Installing memory in the bottom slot

The internal components of your iMac can be warm. If you've been using your iMac, wait ten minutes after shutting it down to let the internal components cool.

After you shut down your iMac and give it time to cool, follow these steps:

1. Disconnect the power cord and all other cables from your computer.
2. Place a soft, clean towel or cloth on the desk or other flat surface to prevent scratching the display.
3. Hold the sides of the computer and slowly lay the computer face-down on the towel or cloth.
4. Using a Phillips screwdriver, remove the RAM access door on the bottom of the iMac and set it aside:
   
5. Move the DIMM ejector clips to their fully open position:
   
6. Insert your RAM SO-DIMM into the bottom slot, keeping in mind the orientation of the keyed SO-DIMM:
   
7. After you insert it, press the DIMM up into the slot with your thumbs. Don't use the DIMM ejector clips to push in the DIMM, as this might damage the SDRAM DIMM. There should be a slight click when you seat the memory fully.
8. Close the ejector clips:
   
9. Reinstall the memory access door:
   
10. Place the computer in its upright position. Reconnect the power cord and all other cables to the computer, then start up the computer.

Replacing memory in the top slot

After you shut down your iMac and give it time to cool, follow these steps:

1. Disconnect the power cord and all other cables from your computer.
2. Place a soft, clean towel or cloth on the desk or other flat surface to prevent scratching the display.
3. Hold the sides of the computer and slowly lay the computer face-down on the towel or cloth.
4. Using a Phillips screwdriver, remove the RAM access door on the bottom of the iMac and set it aside:
   
5. Pull the two levers on each side of the memory compartment to eject the memory module that's already installed:
   
6. Remove the memory module from your iMac as shown below:
   
7. Insert your RAM SO-DIMM into the top slot, noting the orientation of the keyed SO-DIMM:
   
8. After you insert it, press the DIMM up into the slot with your thumbs. Don't use the DIMM ejector clips to push in the DIMM, as this might damage the SDRAM DIMM. There should be a slight click when you seat the memory fully.
9. Close the ejector clips:
   
10. Reinstall the memory access door:
    
11. Place the computer in its upright position. Reconnect the power cord and all other cables to the computer, then start up the computer.

Confirm that your iMac recognizes its new memory

After you install memory, you should confirm that your iMac recognizes the new RAM by choosing Apple menu  > About This Mac.

The window that appears lists the total memory, including the amount of memory that originally came with the computer plus the newly added memory. If all the memory in the iMac has been replaced, it lists the new total of all installed RAM.

For detailed information about the memory installed in your iMac, click System Report. Then choose Memory under the Hardware section in the left side of System Information.

Free Up Memory On Mac Air

If your iMac doesn’t start up after you install memory

If your iMac doesn’t start up or turn on after you install additional memory, check each of following, then try to start your iMac again.

• Verify that the added memory is compatible with your iMac.
• Visually inspect each DIMM to ensure they are correctly installed and fully seated. If one DIMM sits higher or is not parallel to the other DIMMs, remove and inspect the DIMMs before reinstalling them. Each DIMM is keyed and can only be inserted in one direction.
• Confirm that the memory cage levers are locked into place.
• Make sure to let the memory initialization complete during startup. Newer iMac models perform a memory initialization procedure during startup after you upgrade memory, reset NVRAM, or rearrange DIMMs. This process can take 30 seconds or more and the display of your iMac remains dark until the process completes.
• Disconnect all attached peripherals other than keyboard/mouse/trackpad. If the iMac begins working correctly, reattach each peripheral one at a time to determine which one is preventing the iMac from operating correctly.
• If the issue persists, remove the upgraded DIMMs and reinstall the original DIMMs. If the iMac works correctly with the original DIMMs, contact the memory vendor or place of purchase for assistance.

If your iMac makes a tone after you install memory

iMac models introduced before 2017 might make a warning sound when you start up after installing or replacing memory:

• One tone, repeating every five seconds signals that no RAM is installed.
• Three successive tones, then a five-second pause (repeating) signals that RAM doesn't pass a data integrity check.

If you hear these tones, confirm that the memory you installed is compatible with your iMac and that it's installed correctly by reseating the memory. If your Mac continues to make the tone, contact Apple Support.

Optimised Storage helps you save storage space by storing your content in iCloud and making it available on demand:

• When storage space is needed, files, photos, films, email attachments and other files that you seldom use are stored in iCloud automatically.
• Each file stays exactly where you last saved it, and will download when you open it.
• Files that you’ve used recently remain on your Mac, along with optimised versions of your photos.

If you haven't yet upgraded to macOS Sierra or later, learn about other ways to free up storage space.

Find out how much storage is available on your Mac

Choose Apple menu  > About This Mac, then click Storage. Each segment of the bar is an estimate of the storage space used by a category of files. Move your pointer over each segment for more detail.

Click the Manage button to open the Storage Management window, pictured below.

Manage storage on your Mac

The Storage Management window offers recommendations for optimising your storage. If some recommendations are already turned on, you will see fewer recommendations.

Store in iCloud

Click the Store in iCloud button, then choose from these options:

• Desktop and Documents. Store all files from these two locations in iCloud Drive. When storage space is needed, only the files you recently opened are kept on your Mac, so that you can easily work offline. Files stored only in iCloud show a download icon , which you can double-click to download the original file. Learn more about this feature.
  
• Photos. Store all original, full-resolution photos and videos in iCloud Photos. When storage space is needed, only space-saving (optimised) versions of photos are kept on your Mac. To download the original photo or video, just open it.
  
• Messages. Store all messages and attachments in iCloud. When storage space is needed, only the messages and attachments you recently opened are kept on your Mac. Learn more about Messages in iCloud.

Storing files in iCloud uses the storage space in your iCloud storage plan. If you reach or exceed your iCloud storage limit, you can either buy more iCloud storage or make more iCloud storage available. iCloud storage starts at 50 GB for $0.99 (USD) a month, and you can purchase additional storage directly from your Apple device. Learn more about prices in your region.

Optimise Storage

Click the Optimise button to save space by automatically removing films and TV shows you've watched. When storage space is needed, films or TV shows that you've purchased from Apple and have already watched will be removed from your Mac. Click the download icon next to a film or TV show to download it again.

Your Mac will also save space by only keeping recent email attachments on this Mac when storage space is needed. You can manually download any attachments at any time by opening the email or attachment, or saving the attachment to your Mac.

Optimising storage for films, TV shows and email attachments doesn't require iCloud storage space.

Empty Bin Automatically

Empty Bin Automatically permanently deletes files that have been in the Bin for more than 30 days.

Reduce Clutter

Reduce Clutter helps you identify large files and files you might no longer need. Click the Review Files button, then choose any of the file categories in the sidebar, such as Applications, Documents, Music Creation or Bin.

You can delete the files in some categories directly from this window. Other categories show the total storage space used by the files in each app. You can then open the app and decide whether to delete files from within it.

Learn how to re-download apps, music, films, TV shows and books.

Where to find the settings for each feature

The button for each recommendation in the Storage Management window affects one or more settings in other apps. You can also control those settings directly within each app.

• If you're using macOS Catalina or later, choose Apple menu  > System Preferences, click Apple ID, then select iCloud in the sidebar: Store in iCloud turns on the Optimise Mac Storage setting on the right. To turn off iCloud Drive entirely, deselect iCloud Drive.
• If you're using macOS Mojave or earlier, choose Apple menu > System Preferences, click iCloud, then click Options next to iCloud Drive. Store in iCloud turns on the Desktop & Documents Folders and Optimise Mac Storage settings.
• In Photos, choose Photos > Preferences, then click iCloud. Store in iCloud selects iCloud Photos and Optimise Mac Storage.
• In Messages, choose Messages > Preferences, then click iMessage. Store in iCloud selects Enable Messages in iCloud.

• If you're using macOS Catalina or later, open the Apple TV app, choose TV > Preferences from the menu bar, then click Files. Optimise Storage selects “Automatically delete watched films and TV shows”.
• In you're using macOS Mojave or earlier, open iTunes, choose iTunes > Preferences from the menu bar, then click Advanced. Optimise Storage selects “Automatically delete watched films and TV shows”.
• In Mail, choose Mail > Preferences from the menu bar, then click Accounts. In the Account Information section on the right, Optimise Storage sets the Download Attachments menu to either Recent or None.

Empty Bin Automatically: From the Finder, choose Finder > Preferences, then click Advanced. Empty Bin Automatically selects “Remove items from the Bin after 30 days”.

Other ways that macOS helps automatically save space

With macOS Sierra or later, your Mac will automatically take these additional steps to save storage space:

How To I Free Up Memory On Imac Pro

• Detects duplicate downloads in Safari, keeping only the most recent version of the download
• Reminds you to delete used app installers
• Removes old fonts, languages and dictionaries that aren't being used
• Clears caches, logs and other unnecessary data when storage space is needed

Mac Free Memory Command

How to free up storage space manually

Even without using the Optimised Storage features described in this article, you can take other steps to make more storage space available:

• Music, films and other media can use a lot of storage space. Learn how to delete music, films and TV shows from your device.
• Delete other files that you no longer need by moving them to the Bin, then emptying the Bin. The Downloads folder is good place to look for files that you might no longer need.
• Move files to an external storage device.
• Compress files.
• Delete unneeded email: In the Mail app, choose Mailbox > Erase Junk Mail. If you no longer need the email in your mailbox, choose Mailbox > Erase Deleted Items.

Learn more

• The Storage pane of About This Mac is the best way to determine the amount of storage space available on your Mac. Disk Utility and other apps may show storage categories, such as Not Mounted, VM, Recovery, Other Volumes, Free or Purgeable. Don't rely on these categories to understand how to free up storage space or how much storage space is available for your data.
• When you duplicate a file on an APFS-formatted volume, that file doesn't use additional storage space on the volume. Deleting a duplicate file frees up only the space required by any data you might have added to the duplicate. If you no longer need any copies of the file, you can recover all of the storage space by deleting both the duplicate and the original file.
• If you're using a pro app and Optimise Mac Storage, learn how to make sure that your projects are always on your Mac and able to access their files.