The Main Thread is the part of the browser that is responsible for processing paints & user events, making it highly important for webpage speed.

Webmasters should ensure that only essential processes are using the main thread, and that all resources it loads are easily accessible.

When these conditions aren’t met, webpage load speed can be negatively impacted, which is detrimental for user experience & website rankings.

Optimizing Content To Free Up The Main Thread For SEO

Whenever publishing content to a website, it needs to be structured in a way that all of the requests & responses can be handled as quickly & efficiently as possible.

To do this, all files that must load before the page renders above the fold need to be as compact & streamlined as possible.

This can be accomplished by grouping & minifying code such as JavaScript & CSS files, and making sure that any resources such as images or videos that are not used above the fold do not load until they are required.

The easier it is for this content to load, the freer the main thread is, enabling it to process more data & requests in a shorter period of time.

This in turn leads to a more desirable user experience, and ultimately improves rankings as well as SERP exposure, as connectivity issues for end users are less likely to cause it to not be considered for a SERP result.