: If you already have an earlier version of El Capitan installed, you can download the 10.11.6 Combo Update (1.5 GB) to update your system directly. System Requirements
Mac OS X El Capitan (version 10.11.6) is available as a free download from Apple for compatible older Mac models. The 10.11.6 version was the final release of El Capitan, issued on July 9, 2018, to improve stability, security, and compatibility. Official Download Methods Mac OS X El Capitan 10.11.6 Free Download
To install OS X 10.11.6, your Mac must meet these minimum specifications: OS X El Capitan - Technical Specifications - Apple Support : If you already have an earlier version