Understanding Total Blocking Time
Total Blocking Time (TBT) is not an official Core Web Vital metric, but it holds significance as it can be measured using tools like PageSpeed Insights or Lighthouse, unlike First Input Delay (FID). By improving TBT, we can ultimately enhance FID, which is the actual Core Web Vital metric.
If the main-thread remains blocked for an extended period, it leads to a sluggish and unresponsive user experience.
How WP Rocket Can Assist
To optimize TBT, you can follow these steps on your site using PageSpeed Insights or Lighthouse:
- Prefetch DNS requests: Resolving the DNS of a specific domain ahead of explicit usage can help reduce the impact of third-party JS code.
Minimize Main Thread Work
Minifying CSS files and removing unused CSS can significantly reduce main thread work. WP Rocket not only minifies CSS files but also compresses them with GZIP, resulting in smaller file sizes and improved transfer speeds.
Keep Request Counts Low and Transfer Sizes Small
To optimize Google Fonts, WP Rocket automatically optimizes Google font requests with the display=swap parameter and preconnect resource hint.
For self-hosted fonts, you can improve load time by adding a preload tag in the
<head> section of your site. This instructs the browser to initiate font downloads earlier, enhancing overall performance.
Additional Steps to Improve TBT
For more information on improving Core Web Vitals, refer to the WP Rocket Core Web Vitals Hub – First Input Delay.