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FID vs. INP: The Change Is Here

An orange pot of paint against a yellow background

What is the difference between the two? Why is one being replaced? How will this affect my current strategy? How do I prepare for this change? 

As with many changes in regards to Technical SEO, we’re left with lots of questions, and not many answers! Luckily, we have people who eat, breathe and dream SEO – and those people are obsessed with finding out the answers to things they don’t understand – and those people are me. 

Interaction to Next Paint (INP) has now officially replaced First Input Delay (FID) as a Core Web Vital. Everything you need to know about optimising for INP is in this article.

But first

What is a core web vital?

A core web vital is a metric that Google uses to quantify the user experience of a website. There are three basic core web vitals that are used; First Input Delay (Soon to be Interaction to Next Paint), Cumulative Layout Shift, and Largest Contentful Paint. In essence, they are the vital signs of a website. Using tools like Google Lighthouse, Pagespeed Insights, and Search Console, we can determine if our core web vitals are up to par. 

If you’d like to learn more, then check out our article on CWV!

Because everyone likes to know what they’re getting themselves into before they jump in, here’s a quick overview of what we’ll be covering:

Why has INP Replaced FID?

The TL;DR is INP will give a more holistic view of a website’s user experience; in other words, INP will give a more comprehensive view of a website’s responsiveness to users’ interactions by examining how quickly they see the results of their actions

But how?

We all love a list, so here’s a quick one:

  • INP provides a wider understanding of page interactivity. While FID only measures the initial delay between a user’s first interaction with a website and the browser’s response, INP will measure the interactivity throughout a user’s time on a page.
  • FID doesn’t consider the time it takes for essentially interactive scripts to load after the initial page load – INP will measure this.
  • FID doesn’t take into consideration different web applications with complex interactions. INP will be more suitable for determining the performance of dynamic websites.
  • INP will measure the interaction for multiple events, giving a broader view of a page’s interactivity (FID only measures one interaction per event!).

While FID provides valuable insights into user initial interaction delays, INP offers a more comprehensive evaluation of a website’s overall interactivity. By taking into consideration various factors influencing responsiveness, INP better reflects real-world user experiences.

What is INP?

INP (Interaction to Next Paint) measures responsiveness between a user interaction and the time it takes to paint after that interaction. It additionally takes into account all user interactions on a page, rather than just the first.

These interactions include:

  • Mouse clicks
  • Taps (on touch screens)
  • Keystrokes

INP will measure the time it takes for the single longest interaction on the page – this is what gives your INP score.

A good INP score is 200 milliseconds or less between the interaction and the paint. 

INP

As with any change, INP comes with its advantages and disadvantages. Because this is a new metric, it’s likely that the disadvantages will be addressed in the future, but it’s important to consider them at the moment:

  1. You will have to use Chrome as your primary browser if you’d like to measure this data.
  2. It’s not currently supported by third-party services, and so will have to be implemented manually.
  3. It may not measure delays in responsiveness caused by internal factors like ads or JavaScript widgets.

What are the differences between INP and FID?

INP measures the longest interaction within a series of interactions while FID measures the length of the first interaction

Let’s put this into a practical example:

<User Interaction Begins>

  • You arrive on a webpage – it loads quickly
  • You click on an image carousel to look through photos – they load easily after each click
  • You scroll down the page – there’s no delay
  • You arrive at a form  – you’d like to fill it out
  • You click the fields in the form and begin to fill them out – but it takes half a second before anything you type appears in the form
  • You submit the form

<User Interaction Ends>

In this case, FID would come back with a positive score – which isn’t necessarily a true report of the page responsiveness. The carousel loaded quickly when the user clicked through the photos. That’s your FID!

FID won’t take into consideration the delay that happened while typing into the form. This is where INP comes in – it will take into account that delay if it was the longest delay on the page for that user.

What are the similarities between INP and FID?

We’re always focusing on our differences, huh? Let’s change that by taking a look at what INP and FID have in common. This can help us build an overall picture of what exactly INP is.

Both INP and FID measure user interaction time, and both aim to improve user experience. Additionally, they both detect delays in user interaction and the responsiveness of that interaction – though FID only measures the initial interaction with a page, while INP measures all interactions.

In reality, an INP score and an FID score can be used together to determine a page’s responsiveness. FID can give you an idea of the response delay of a page immediately after loading, while INP gives a broader view of response delays.

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How to Measure INP using GSC

INP can be measured using Google Search Console and Page Speed Insights.

With GSC, navigate to the Page Experience tab on the left. From here you can click on the “Core Web Vitals” button below either desktop or mobile. Scroll down and you will see a section entirely dedicated to INP.

prepare for changes coming in March 2024

For Pagespeed Insights, enter the URL, like you normally would, and INP will show as a metric underneath First Input Delay.

First input delay and Interaction to next paint

How to Optimise for INP

Now we’ve made it. We know what INP is, we know what to expect from a good INP score, and we know why we’re measuring INP. Now what do we do?

Optimising for INP is similar to other core web vital metrics in the sense that you monitor the score, prioritise pages, make fixes and validate the fixes. 

To Optimise for INP:

  • Keep an eye on the score using GSC. This will give you an overall look at all the CWV metrics and all the URLs that will need to be optimised. 
  • Prioritise the pages that need to be optimised. Pages with high traffic and low INP scores should be a top priority. Pages that convert users to paying customers should also be considered a priority. 
  • Send this information to the development team, with suggestions on how to improve the INP score.
    • Suggestions can include: reducing page sizes, optimising images and scripts, caching static resources, etc
  • Once these fixes are implemented, have GSC validate the fixes. 

Final Thoughts

Obviously, change is scary, but knowing how to handle these changes can be empowering. Hopefully you found everything you need to know to start optimising, however, if you’re still unsure how to go about these fixes, then get in touch! We have a dedicated (and very friendly) team of experts who can help address any technical SEO issues you may be facing. 

Katja Kline

Katja Kline

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