This can also be another major cause of a poor score in the total blocking time metric on Google PageSpeed insights. With third party JavaScript, you only want to load essential scripts. If you can choose to remove the script from your website, or serve it locally that’s the best bet. Your website is probably loading third party JavaScript from multiple sources. If you use Google analytics, you’re loading third party JavaScript, if you use stripe or PayPal payment processing, you’re loading third party JavaScript, and the list goes on and on.

Removing these scripts is typically impractical or impossible to do, so efficiently loading third party JavaScript is the best remedy. Unless your script has to run before the page renders, you should always load it asynchronously or defer it. The way you do this is by adding async or defer tags on the script element. However, if you’re a casual WordPress user, this may be difficult as it could be hard coded into your themes or plugins. That means changing it on a code level doesn’t make any sense, as every update to a plugin or theme would overwrite it. This is where our favorite performance optimization comes to work – asset cleanup. For individual JavaScript files, we choose to load it asynchronously or defer it.