Chrome Drops FID, Prioritizes INP for User Interaction Metrics

Google Chrome has officially ended support for its First Input Delay (FID) metric, marking a huge step toward improving web performance measurement. 

Developers are now urged to fully transition to Interaction to Next Paint (INP), a more comprehensive metric that evaluates a user’s interaction with a webpage from input to visual feedback.

Google’s New Focus

Google’s decision to discontinue FID directly responds to its narrow measurement capabilities. FID only looked at the delay between a user’s action (such as clicking a button) and the browser’s response.

Although this data was useful in identifying certain performance problems, it did not account for other aspects of the interaction, such as how long it took the webpage to update visually after the user’s input.

Interaction to Next Paint (INP) corrects this oversight by offering a more holistic view of interaction performance. Instead of focusing on the first response, INP measures the entire sequence—from when a user interacts with a webpage until the page visually updates. 

Today’s the day: Chrome ends support for FID

If you’re still relying on it in Chrome tools, your workflows WILL BREAK

We’re all-in on INP!https://t.co/sc6utE44MN

— Rick Viscomi (@rick_viscomi) September 10, 2024

Developers can now pinpoint more intricate performance bottlenecks that FID would have overlooked. INP effectively tracks input, processing, and rendering delays, providing a fuller picture of how users experience the web.

What Happens to Tools That Tracked FID?

With FID now retired, several prominent performance tools integral to web development will no longer support the metric. 

For instance, PageSpeed Insights in Chrome, a vital tool for developers trying to optimize their websites, has already stopped providing FID data in its real-user experiences area.

The Chrome User Experience Report (CrUX), widely used to track field data on web performance, will no longer report FID data through its API or BigQuery project. Changes are rolling out this month.

The widely used web-vitals.js library is another tool affected by FID’s retirement. Version 5.0 of the library, set to be released soon, will remove the onFID function, signaling a clear break from the outdated metric. 

Developers using this library to monitor Core Web Vitals must update their code to accommodate these changes.

Additionally, the Web Vitals extension, a tool commonly used to track web performance metrics, will cease reporting FID in any of its outputs, including the overlay panel and console logs. 

This means developers who rely on these tools must transition to INP to continue measuring and optimizing interaction performance effectively.

As part of the transition, the FID documentation on Google’s web.dev platform is restructured. 

The article on FID will remain available, but with a clear warning that it is outdated and should not be used for future performance assessments. 

More importantly, Google’s Optimize FID guide will permanently redirect to Optimize INP, ensuring developers can access the latest best practices.

The affected tools include

Page Speed Insights
Chrome UX Report
web-vitals.js
Web Vitals extension

Only web-vitals.js will have a major version bump (5.0)

CrUX BigQuery will be updated in the next release (202409 in October)

The rest will end support over the next few days

— Rick Viscomi (@rick_viscomi) September 10, 2024

The Technical Benefits of Interaction to Next Paint

One of the key advantages of INP is its ability to track the full lifecycle of user interaction, offering developers more actionable insights into web performance. 

Unlike FID, which only tracked the delay before the browser’s first response to user input, INP measures three critical phases of an interaction:

• Input delay – The time from when a user initiates an action (e.g., clicks a button) to when the browser begins processing it.
• Processing delay is the time it takes for the browser to process the input and run the associated event handlers.
• Rendering delay is the time it takes for the browser to update the page visually in response to the input.

This approach helps developers identify and fix performance bottlenecks that affect a webpage’s responsiveness. 

Key Timeline and Next Steps for Developers

Google has thoughtfully planned FID’s retirement over the past year, ensuring developers have ample time to adjust. In May 2023, FID was officially replaced by INP as a Core Web Vital, setting the stage for this final retirement. 

The full deprecation of FID across all Chrome performance tools is now complete, but developers must take immediate steps to ensure their websites remain optimized under the new INP metric.

Beginning in October 2024, the CrUX BigQuery project will remove FID-related fields from its schema, focusing solely on INP. Historical data on FID will remain available for developers interested in past performance trends, but new data will prioritize INP, providing a clearer view of current web performance.

To help developers transition, Google has updated its resources on web.dev, offering detailed guidance on optimizing websites for INP. 

Developers are encouraged to audit their sites using tools like PageSpeed Insights or CrUX and identify areas for improving INP performance. 

Updating custom scripts or performance monitoring tools that currently rely on FID is also crucial, as they must be reconfigured to work with INP.

Adapting to the New Web Performance Standard

Beyond merely altering measurements, Google’s discontinuation of FID shows a larger commitment to improving the online user experience. User interactions in web applications must be smooth and seamless as they get more complicated, particularly given the growing demand for responsive, fast-loading websites. INP addresses these demands by providing a clearer, more actionable view of how users experience interactions on a webpage.

Developers must embrace this new standard and take steps to optimize their websites for INP. The Optimize INP guide offers best practices for optimizing INP and concrete steps for reducing interaction delays.

Take Action: What Developers Should Do Now

The transition from FID to INP is not just an update for developers; it’s a necessity to stay competitive in the ever-evolving digital economy. Here’s what to focus on:

Learn About INP: Visit Google’s web.dev platform to understand how INP works and how it differs from FID.

Audit Website Performance: Use tools like PageSpeed Insights or CrUX to audit your site’s current performance under INP.

Update Monitoring Tools: If you are using tools like web-vitals.js, be prepared to update your code for version 5.0, which no longer supports FID.

Plan for CrUX Changes: If your site relies on the CrUX BigQuery dataset, ensure your data pipelines are updated to accommodate the removal of FID fields starting in October 2024.

Optimize Responsiveness: Apply best practices outlined in the Optimize INP guide, focusing on reducing delays across the input, processing, and rendering phases.

Key Takeaways

• Chrome has officially discontinued support for the First Input Delay (FID) metric and replaced it with the more comprehensive Interaction to Next Paint (INP) metric.
• Several performance tools, including PageSpeed Insights, CrUX, and web-vitals.js, will no longer report FID data, pushing developers to adopt INP.
• INP offers a more accurate view of user interaction by measuring the entire process from input to visual update.
• Developers should audit their websites, update their monitoring tools, and consult Google’s Optimize INP guide for best practices.
• The end of FID reflects Google’s ongoing efforts to improve web performance and enhance user experiences on the web.