With WordPress 4.3 and on, you can add a favicon or site icon from the WordPress admin area:

  • Prepare image. The site icon image should be a square; you can also use a rectangular image. and WordPress will allow you to crop the image once you add it.
  • Go to Appearance > Customize and click on the 'Site Identity' tab.
  • Click on the select image button. Then, upload the image you want to use as favicon.