Apple’s older OS installers (Yosemite, El Capitan) were signed with security certificates that expired in late 2019 and early 2020. When you try to launch a downloaded installer from 2019 or earlier, macOS now rejects it with a “damaged” error — even if the file is perfectly fine.
| Test | Expected result |
|------|----------------|
| Mount DMG | No mount error. Contains .app or InstallMacOSX.pkg |
| Verify signature | codesign -vvv Install\ OS\ X\ El\ Capitan.app → should pass |
| Create bootable USB | createinstallmedia works without “expired” message after date set back |
| Installation | No “This copy of the Install OS X El Capitan application is damaged” error |
If the fixed DMG passes these, it is functionally identical to Apple’s original. mac os x el capitan 10116 installer dmg download fixed
macappstore://showUpdatesPage?productId=1147394723Verification: The correct DMG should have the following checksums (SHA-1):
InstallMacOSX.dmg (10.11.6 – 15G31) – SHA-1: e2c61739ed1cceeeb8a9a8ffb3d9fbfab9be897d
If your checksum does not match, do not proceed. Apple’s older OS installers (Yosemite, El Capitan) were
After you open the DMG and drag the .app into your /Applications folder, launching it directly will fail (certificate expiration). Here is the fixed terminal command to bypass the date check:
Important: Do not close the installer once it starts. Setting the date back mid-installation will break the process. Click that link — it will open the
You asked for a .dmg file. It is important to note that Apple distributes the installer as an application bundle (.app), not a raw DMG. However, you can easily create a bootable DMG or USB drive from that file.