If you have previously "purchased" (downloaded) El Capitan using your Apple ID, it will appear in your tab in the App Store. However, this is increasingly rare for modern users to find. Creating a Bootable USB (The Pro Method)

Before you spend time downloading, ensure your hardware is compatible. El Capitan generally supports: Early 2008 or newer MacBook Air: Late 2008 or newer MacBook Pro: Mid 2007 or newer iMac: Mid 2007 or newer Mac Mini: Early 2009 or newer Mac Pro: Early 2008 or newer Safety Warning: Avoid Third-Party Sites

Released in July 2016, version 10.11.6 was the final "polishing" update for El Capitan, focusing on security, stability, and compatibility. Here is everything you need to know about downloading and installing it safely today. Why El Capitan Still Matters

While many third-party sites offer "cracked" or "direct" links, the safest method is always to go through Apple. Apple provides a direct download for El Capitan because it is often necessary to restore older machines. 1. The Official Apple Support Link

Once you have the installer in your Applications folder, the best way to use it is by creating a bootable USB drive. This allows you to perform a "clean install," which wipes away years of system junk. A USB drive with at least 12GB of space.

As the final build, 10.11.6 is remarkably bug-free compared to its predecessor, Yosemite. Where to Download the Official 10.11.6 DMG

Mac OS X 10.11 El Capitan serves as a vital "bridge" OS. For many older Macs, it is the highest possible OS they can run. For others, it is a required stepping stone before upgrading to High Sierra or Mojave. Key features that keep users coming back include: The ability to work in two apps side-by-side.

Apple often provides this as a .dmg file containing a .pkg installer.

Improvements in app launching and PDF rendering via Metal.