As you can see - this feature is incredibly powerful and can dramatically improve PageSpeed scores as well as overall page load times.
Before you activate Delay Javascript Execution across your site - we do urge caution as there are a few things you need to be aware of:
Impact on Tracking & Analytics Scripts
If you enable Delay Javascript on your tracking and analytics scripts (for example Google Analytics or Google Tag Manager) you should be aware that any visitors that do not interact with your page will not be tracked.
This is because the script is not rendered to the page which logs them as a visitor. This can have an impact on your tracked visitor figures and may result in a drop in your analytics. It may also limit your ability to track visitors from paid traffic sources.
In most cases we find that visitors will interact with the page in some way, but if a visitor immediately clicks back on their browser it's possible they may not be tracked.
External Scripts No Longer Working
Although we've done everything we can to ensure that this feature works with different scripts you might use on your site - it's possible this feature could stop certain scripts from working or features on your website that require codes to be rendered upon page load.
We always urge you test your pages after activating the feature - or activate it on one page first using the on-page optimization options panel before activating it sitewide.
If you find a script is not working - you can use our exclude feature to stop that script being affected by the Delay JS feature...
How to exclude a script
To help you customize your use of the Delay Javascript feature, we provide an exclusion list so you can exclude any files you don't want to be optimized by this feature