When you are using the Facebook Pixel for tracking how effective the Facebook advertising campaign that might be running for your site the request can slow down the load time of your site. In the case of the Facebook Pixel tracking code, it can add almost up to a second on the site’s load time when you are testing the site using site load testing like GTmetrix or WebPageTest.
The simplest way to improve the Facebook Pixel load times on your site is to use the Flying Scripts plugin. After you have installed and activated the Flying Scripts plugin on your site it will add a new admin menu too;
Settings > Flying Script
The keyword to add into the plugin’s settings for the Facebook Pixel is fbevents.js. You can set the timeout for when there is no user interaction on the site.