A favicon is an icon for a site that is displayed in the browser window and in bookmarks, including on mobile devices. The new Site Icon module in the popular Jetpack plugin allows you to add a favicon to your WordPress site.
If you have not used the Jetpack plugin before, then you need to install and activate it first. Once activated, the Jetpack plugin needs to be linked to your WordPress.com network account by following the instructions in the Jetpack section of the WordPress Dashboard. Remember that your WordPress account and the WordPress.com network are two different things.
Site Icon Module for Favicon
In the Settings section of the Jetpack plugin, you need to find the Site Icon module (or “Site Icon”) and activate it, after which a new item “Site Icon” will appear at the very end of the page in the Settings → General section of the WordPress administration panel.
To add a favicon to your site, click on the “Add Site Icon” button and upload an image that is at least 512 pixels wide and tall. Once the image is uploaded, Jetpack will offer to crop the favicon and also show you how the favicon will look in the browser and on mobile devices.
After saving the changes, Jetpack will generate all the required dimensions for the given image and add the required meta tags to the site so that the new icon is displayed in the browser. Please note that many browsers (and search engines) cache favicon images, so changes may not take effect immediately.
This module also works well in Multisite mode, where each individual site on the network needs its own favicon. You can replace the selected icon or delete it in the Options → General section.
Finally, it should be noted that the ability to upload your own favicon may in the future appear in the very core of WordPress. Although we do not recommend hoping and waiting for this, discussions have been going on for more than 4 years.