From El Capitan to Yosemite

You'll need to make a Yosemite USB installer. USB stick/external drive needs to be at least 8GB and a USB3 one will be much quicker.

First download the OS X 10.10 Yosemite installer from the Mac App Store in the Purchases section (you may need to hold alt/option while selecting Purchases. Once it's downloaded, just quit the installer and set the downloaded file's name to InstallOSXYosemite.app (make sure only .app, not .app.app)

• Plug in your USB drive into the computer and open Disk Utility (in Applications).
• Select the USB drive from the left sidebar and click on Erase tab.
• Choose Mac OS Extended (Journaled) in the format box and set the name be YosemiteInstaller
• Now click on Erase button and wait until the format process completes.
• Then choose Partition tab and select 1 Partition from Partition Layout dropdown menu. Click on Option and ensure GUID Partition Table is selected as the partition scheme, with its name set to YosemiteInstaller.
• Launch the Terminalapp (in Applications/Utilities) and copy-paste the following command in, and then hit Enter:

  sudo /Applications/InstallOSXYosemite.app/Contents/Resources/createinstallmedia --volume /Volumes/YosemiteInstaller --applicationpath /Applications/InstallOSXYosemite.app --nointeraction

• This will create the bootable USB flash drive. This takes between 10-20 minutes. Do not interrupt the Terminal or eject the flash drive during the process. Once the process completes, you will see the message "Copy Complete. Done."

The OS X Yosemite bootable USB flash drive will be ready for use and you can start the clean installation process.

How to Clean Install OS X Yosemite on Your Mac

• Ensure the bootable USB flash drive is plugged into your Mac and restart the computer. As soon as the start-up chime plays, press the Option key (Alt).
• Choose the USB drive on the start-up drive selection screen and hit Enter/Return on the keyboard.
• Wait until the Yosemite installer appears on screen. This could take a few seconds or minutes.
• Click on Disk Utility and then hit Continue.
• Click on Macintosh HD from the left hand-side pane and then hit Erase tab on the top-right portion of the window. Leave all the settings at their default values and then hit Erase button at the bottom right. This will wipe all files stored on your startup hard drive.
• When the erasing process is complete, return to the first screen where you selected Disk Utility. Now click on Install OS X and then hit Continue.
• Choose the Macintosh HD partition you erased in step 5 and then click Install.

Do I loose all the data and programs??

Without a backup, yes. But you can copy over your data to a safe place before erasing El Capitan and you can re-download your apps from the App Store once you're back on Yosemite.

Does this have to be an external USB key? Or can I simply create a partition on my computer's SSD?

See my answer to your own thread.

the yosemite download is stuck on "paused." What do I do from there? Also, Im using my 64gb flashdrive for the installer but it won't allow me to select the partition button.

Where do i get Yosemite install file its not available in my app store.

Cant find it in my purchases Not even after holding opt.

Hi Max108,

I have done the step to the letter but when i copy and paste the code to the terminal with no spaces all i get is

"-bash: sudo/Applications/InstallOSXYosemite.app/Contents/Resources/createinstallmedia--volume/Volumes/YosemiteInstaller--applicationpath/Applications/InstallOSXYosemite.app--nointeraction: No such file or directory"

Please help I just bought my airbook at the end of last year for school work and ever since i upgraded to El Capitan its been running extreamly slow and freezing up I have re installed El Capitan 3 times as per Apple help over the phone and nothing :-(.

I really need Yosemite back in my computer.

I knowknow what im doing wrong nor what should i do to fix it

Thank you

First, you need to go to the app store and download Yosemite. When the download completes

then you can run the terminal command.