Install memory in an iMac

Get memory specifications and find out how to install memory in iMac computers.

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.

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

Get memory specifications for iMac (Retina 5K, 27-inch, 2020), then find out 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 have the same capacity and speed, and be from the same vendor. Use small outline dual inline memory modules (SO-DIMM) that meet all of these criteria:

• PC4-21333

• Unbuffered

• Non-parity

• 260-pin

• 2666 MHz 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 find out 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

• Non-parity

• 260-pin

• 2666 MHz DDR4 SDRAM

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

Get memory specifications for iMac (Retina 5K, 27-inch, 2017), then find out 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:

• PC4-2400 (19200)

• Unbuffered

• Non-parity

• 260-pin

• 2400 MHz DDR4 SDRAM

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

Get memory specifications for iMac (Retina 5K, 27-inch, Late 2015), then find out 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

• Non-parity

• 204-pin

• 1867 MHz DDR3 SDRAM

For these 27-inch models

Get memory specifications for the following iMac models, then find out 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

• Non-parity

• 204-pin

• 1600 MHz DDR3 SDRAM

Installing memory

After you've shut down your iMac and given it some time to cool down, follow these steps:

1. Disconnect the power cable and all other cables from your computer.

2. Place a soft, clean towel or cloth on a desk or other flat surface to prevent the display from getting scratched.

3. Hold the sides of the computer and slowly place 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-hand sides of the memory cage. Push the two levers outwards to release the memory cage:

   

7. After the memory cage has been released, pull the memory cage levers towards 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 insert fully:

   

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 you align the notch on the DIMM with 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 to the left of centre. If your DIMMs are mixed in capacity, minimise 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 to the 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’ve installed 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 cable and all other cables to the computer, then start up the computer.

For these 27-inch and 21.5-inch models

Get memory specifications for the following iMac models, then find out 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:

Installing memory

After you've shut down your iMac and given it some time to cool down, follow these steps:

1. Disconnect the power cable and all other cables from your computer.

2. Place a soft, clean towel or cloth on a desk or other flat surface to prevent the display from getting scratched.

3. Hold the sides of the computer and slowly place the computer face down on the towel or cloth.

4. Using a Phillips screwdriver, remove the RAM access door on 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, pull the tab gently 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've inserted 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 cable 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 find out 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 1 GB or 2 GB RAM module in each slot for iMac (Mid 2007) and iMac (Early 2008). Use 1 GB, 2 GB or 4 GB 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

After your iMac has cooled down, follow these steps:

1. Disconnect the power cable and all other cables from your computer.

2. Place a soft, clean towel or cloth on a desk or other flat surface to prevent the display from getting scratched.

3. Hold the sides of the computer and slowly place the computer face down on the towel or cloth.

4. Using a Phillips screwdriver, remove the RAM access door on 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've inserted it, press the DIMM up into the slot. There should be a slight click when the memory has been seated 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 cable 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 find out 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 the best performance, fill both memory slots, installing an equal memory module in each slot.

Installing memory in the bottom slot

After you've shut down your iMac and given it some time to cool down, follow these steps:

1. Disconnect the power cable and all other cables from your computer.

2. Place a soft, clean towel or cloth on a desk or other flat surface to prevent the display from getting scratched.

3. Hold the sides of the computer and slowly place 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, bearing in mind the orientation of the keyed SO-DIMM:

   

7. After you've inserted 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 can damage the SDRAM DIMM. There should be a slight click when the memory has been seated correctly.

8. Close the ejector clips:

   

9. Reinstall the memory access door:

   

10. Place the computer in its upright position. Reconnect the power cable and all other cables to the computer, then start up the computer.

Replacing memory in the top slot

After you've shut down your iMac and given it some time to cool down, follow these steps:

1. Disconnect the power cable and all other cables from your computer.

2. Place a soft, clean towel or cloth on a desk or other flat surface to prevent the display from getting scratched.

3. Hold the sides of the computer and slowly place 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've inserted 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 can damage the SDRAM DIMM. There should be a slight click when the memory has been seated correctly.

9. Close the ejector clips:

   

10. Reinstall the memory access door:

    

11. Place the computer in its upright position. Reconnect the power cable and all other cables to the computer, then start up the computer.

Confirm that your iMac recognises its new memory

After you've installed memory, you should confirm that your iMac recognises 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-hand side of System Information.

If your iMac doesn’t start up after you've installed additional memory

If your iMac doesn’t start up or turn on after you've installed additional memory, check each of the 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 have been installed correctly and are fully seated. If one DIMM is sitting higher or is not parallel with 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 you allow the memory initialisation process to finish during startup. Newer iMac models perform a memory initialisation procedure during startup after you've upgraded memory, reset NVRAM or rearranged DIMMs. This process can take 30 seconds or longer, and the display of your iMac will remain dark until the process has finished.

• Disconnect all attached peripherals other than the keyboard, mouse or trackpad. If the iMac starts 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've installed memory

iMac models introduced before 2017 may 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've installed is compatible with your iMac and that it's been installed correctly by reseating the memory. If your iMac continues to make the tone, contact Apple Support.