There is no downgrade, it has to be a clean install on either your current HD or another drive or another partition. You will also either need:

• to currently own El Capitan AND have it in your possession in some way, shape or form.

Rapido y facil podes hacer un pendrive booteable con el programa transmac. Si tenes una Mac y no tiene lectora de DVD aca te explico como hacer un pendrive booteable y como hacer para bootear. For those that have recently updated to OS X El Capitan, you may think that OS X El Capitan volume sound not working. Many by Apple users have reported of audio problems that after upgrading to OS. – Fixes an issue that caused USB audio devices to. Those are recommended updates if you’re not running El Capitan, both available from the  Apple menu. Bootable USB Stick - macOS X El Capitan 10.11 - Full OS Install, Reinstall, Recovery and Upgrade SANDISK USB FLASH DRIVE 2.0/3.1 - 16GB - 5 years warranty Latest certificate (expires These USBs are NOT produced by Apple. Therefore, you can create bootable USB for your Mac using Transmac on windows 10/7/8/8.1 here you will learn the easiest method of creating bootable USB. As you know that Mac OS EL Capitan is the newest version among Mac. In here just follow my steps to create a bootable USB installer for your Mac. Is the twelfth major of the Mac operating system.

• your computer shipped with it when purchased and it would be available from Apple using Recovery.

• A computer that was eligible for El Capitan but not any OS X variants after El Capitan.

if your computer was eligible for Sierra and you did not download El Capitan you may no longer be able to get it from the Apple Store as an option. In this event only Sierra and High Sierra would be downloadable unless you have another Apple Computer that is eligible to upgrade to El Capitan and currently has an OS installed that predates it and is not eligible for Sierra, in which case El Capitan should be available to you from the Ap Store

Before you proceed first backup

then create a bootable instance of El Capitan

Either with directions from Apple

or use a 3rd party solution

Os X El Capitan Bootable Usb Command Not Found

Os X El Capitan Bootable Usb From Windows

then format the drive from Disk Utility in Recovery mode

then install the USB bootable devices image to a new partition
(or you will need to reformat your current drive if it's your only option for an install.)

then use Migration Assistant to restore you account and 3rd party applications to your system.

Os X El Capitan 10.11.0 Bootable Usb (dmg File) (15a284)

Sep 25, 2017 12:39 PM

To get the latest features and maintain the security, stability, compatibility, and performance of your Mac, it's important to keep your software up to date. Apple recommends that you always use the latest macOS that is compatible with your Mac.

Learn how to upgrade to macOS Big Sur, the latest version of macOS.

Check compatibility

The version of macOS that came with your Mac is the earliest version it can use. For example, if your Mac came with macOS Big Sur, it will not accept installation of macOS Catalina or earlier.

If a macOS can't be used on your Mac, the App Store or installer will let you know. For example, it might say that it's not compatible with this device or is too old to be opened on this version of macOS. To confirm compatibility before downloading, check the minimum hardware requirements:

• macOS Catalina 10.15 hardware requirements
• macOS Mojave 10.14 hardware requirements
• macOS High Sierra 10.13 hardware requirements
• macOS Sierra 10.12 hardware requirements
• OS X El Capitan 10.11 hardware requirements
• OS X Yosemite 10.10 hardware requirements

Download macOS using Safari on your Mac

Safari uses these links to find the old installers in the App Store. After downloading from the App Store, the installer opens automatically.

• macOS Catalina 10.15 can upgrade Mojave, High Sierra, Sierra, El Capitan, Yosemite, Mavericks
• macOS Mojave 10.14 can upgrade High Sierra, Sierra, El Capitan, Yosemite, Mavericks, Mountain Lion
• macOS High Sierra 10.13 can upgrade Sierra, El Capitan, Yosemite, Mavericks, Mountain Lion

Safari downloads the following older installers as a disk image named InstallOS.dmg or InstallMacOSX.dmg. Open the disk image, then open the .pkg installer inside the disk image. It installs an app named Install [Version Name]. Open that app from your Applications folder to begin installing the operating system.

• macOS Sierra 10.12 can upgrade El Capitan, Yosemite, Mavericks, Mountain Lion, or Lion
• OS X El Capitan 10.11 can upgrade Yosemite, Mavericks, Mountain Lion, Lion, or Snow Leopard
• OS X Yosemite 10.10can upgrade Mavericks, Mountain Lion, Lion, or Snow Leopard