When you’re ready to install OS X Yosemite (10.10), download it from theMac App Store.
Apple no longer offers Yosemite (10.10) for download.
The information in this article is maintained for archival purposes.
Apple, Inc.
All your user data and any applications that you installed will be gone.
Many of these problems can occur over the years of using your Mac.
As you upgrade systems and applications, debris is left behind and files become large.
This causes slowdowns and may corrupt some system files.
Finding these bits of file debris is almost impossible.
Sometimes, the cure may be worse than the problems.
Performing a clean install deletes all the data on the destination drive.
However, if a clean install cures the problems, the tradeoff may be worth it.
A recentTime Machine backupis the bare minimum you should have on hand.
Also, considercreating a clone of your startup drive.
The YosemiteMigration Assistantworks with cloned drives and lets you easily move data you may need.
Navigate to the OS X Yosemite download page by searching the App Store for Yosemite.
Once you locate OS X Yosemite, select theDownloadbutton.
You may be asked to sign in if you haven’t done so.
When the download is complete, the OS X Yosemite Install app launches on its own.
Do not proceed with the installation.
Instead, quit the installer by selectingQuit Install OS Xfrom theInstall OS Xmenu.
To erase and reformat the startup drive, start your Mac from another equipment.
Instead, plug the flash drive into one of the USB ports on the Mac.
Restart the Mac while holding down theOptionkey.
The OS X Startup Manager appears on the display, showing the devices you might boot the Mac from.
After a short time, you’ll see the Yosemite installer’s Welcome screen.
pick the language you want to use for the installation and then selectContinue.
Disk Utility opens, with the Mac’s drives listed in the left pane.
go for the Mac’s startup drive, usually namedMacintosh HD,andselect theErasetab in the right pane.
You are about to erase your Mac’s startup drive and all of its contents.
verify you have a current backup of this data before proceeding.
Use theFormatdrop-down menu to ensure thatMac OS Extended (Journaled)is selected and then selectErase.
You’re asked if you want to erase the Macintosh HD partition.
The startup drive is completely erased.
Once the process is complete, selectQuit Disk Utilityfrom theDisk Utilitymenu.
You’re returned to the OS X Utilities window.
You’re now ready to start the OS X Yosemite installation process.
In the OS X Utilities window, selectInstall OS Xand then selectContinue.
The OS X Utilities window is dismissed, and the Install OS X app launches.
The Yosemite software licensing terms display.
Read through the licensing terms and selectAgree.
A panel displays, asking you to affirm that you read and agree to the terms.
The installer displays the drives it’s possible for you to install OS X Yosemite on.
Highlight the drive you want to be the OS X Yosemite startup drive and then selectInstall.
The installer prepares the Mac for the installation of OS X Yosemite by copying files to the startup drive.
Once the copying process is complete, the Mac restarts.
An ongoing estimate of the time remaining until the restart displays during the file copy process.
The first phase of the installation process, including the restart, continues without any input required from you.
Be prepared to wait.
With all the files copied, a second restart occurs.
The Mac boots to OS X Yosemite, starts the setup assistant, and displays a welcome screen.
opt for country for the installation and then selectContinue.
pick the keyboard layout to use and then selectContinue.
At this time, we suggest selecting theDon’t transfer any information nowoption.
Sign in with your Apple ID/Apple Account.
If you intend to use any of these services, signing in now is a timesaver.
However, it’s possible for you to skip this step and sign in to those services later.
We’re going to assume that you want to sign in with your Apple Account.
Fill in the requested information and selectContinue.
SelectAgreeto continue, then confirm the agreement by selectingAgreeagain.
It’s now time to create your administrator account.
drop your full name and an account name.
We suggest using an account name with no spaces, no special characters, and no uppercase letters.
Make your selection and then selectContinue.
The process of setting up the iCloud Keychain system is a bit involved.
We recommend using our guide tosetting up and using iCloud Keychainat a later time.
SelectSet Up Laterand selectContinue.
You’re asked if you wish tomake use of iCloud Drive.
The new version of iCloud Drive isn’t compatible with older versions.
Make your selection and selectContinue.
Your Mac finishes the setup process and then displays your new OS X Yosemite desktop.
Have fun, and take time to explore all the new features.
