First Input Delay

The First Input Delay metric aims to measure the delay during the first input.

This metric is available in RUM & synthetic monitoring, but not in soft navigations.
FID will no longer be part of Core Web Vitals after March 12.

Nuances of the First Input Delay metric

There are some important nuances when it comes to the First Input Delay metric:

  • Single Page Applications
    If your site is a Single Page Application, there are exceptions when it comes to tracking Core Web Vitals across all page navigations.
  • only the first interaction
    The metric perfectly described what is does: it only collects data related to the first interaction, while a typical webpage has way more interactions.
  • only the input delay
    And it's only collecting the input delay, while there are many more tasks involved with user interaction that could (cumulatively) build up to a long delay after a user interaction.

The above are reasons why Google was working on and introduced the INP metric.

Replaced by INP

On January 31st, Google announced that on, March 12 INP will become part of Core Web Vitals. It is replacing the FID metric, meaning that FID will then no longer be a Core Web Vitals metric.

Moreover, the Google docs are stating that it will be removed from other tools.

Continue reading about First Input Delay

Want to learn more about First Input Delay? Check our blog, check the FID article or keep an eye out on the changes to the FID metric.