In a recent episode of the Search Off The Record podcast, it was revealed that Google’s rendering system now pretends to be “idle” to trigger certain JavaScript events and improve webpage rendering.
The podcast features Zoe Clifford from Google’s rendering team, who discussed how the company’s web crawlers deal with JavaScript-based sites.
This revelation is insightful for web developers who use such methods to defer content loading.
Google’s “Idle” Trick
Googlebot simulates “idle” states during rendering, which triggers JavaScript events like requestIdleCallback.
Developers use this function to defer loading less critical content until the browser is free from other tasks.
Before this change, Google’s rendering process was so efficient that the browser was always active, causing some websites to fail to load important content.
Clifford explained:
“There was a certain popular video website which I won’t name…which deferred loading any of the page contents until after requestIdleCallback was fired.”
Since the browser was never idle, this event wouldn’t fire, preventing much of the page from loading properly.