upgrading from El Capitan to Big Sur for Macbook (15-inch Early 2011)

macOS Big Sur 11

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Check compatibility

macOS Big Sur is compatible with the following computers. If your Mac isn't compatible, you might be able to install an old version of macOS instead.

MacBook introduced in 2015 or later

MacBook Air introduced in 2013 or later

MacBook Pro introduced in late 2013 or later

Mac mini introduced in 2014 or later

iMac introduced in 2014 or later

iMac Pro

Mac Pro introduced in 2013 or later

https://support.apple.com/en-us/HT201475

How to get old versions of macOS

If your Mac isn't compatible with the latest macOS, you might still be able to upgrade to an earlier macOS, such as macOS Catalina, Mojave, High Sierra, Sierra, or El Capitan.

      To confirm compatibility before downloading, check the minimum requirements for

       macOS Catalina, Mojave, High Sierra, Sierra, El Capitan, or Yosemite.

      You can also find compatibility information on the product-ID page for

       MacBook Pro, MacBook Air, MacBook, iMac, Mac mini, or Mac Pro.

https://support.apple.com/en-us/HT211683

Mac Hardware Requirements

For details about your Mac model, click the Apple icon at the top left of your screen, choose About This Mac. These Mac models are compatible with macOS High Sierra:

• MacBook (Late 2009 or newer)
• MacBook Pro (Mid 2010 or newer)
• MacBook Air (Late 2010 or newer)
• Mac mini (Mid 2010 or newer)
• iMac (Late 2009 or newer)
• Mac Pro (Mid 2010 or newer)

https://support.apple.com/kb/SP765?locale=en_US