Impact on INP due to GTM

[chandra2607]

Summary

High INP Scores Due to GTM Event Processing

Issue Summary

Experiencing high Interaction to Next Paint (INP) scores (Core Web Vitals) when using Google Tag Manager with @next/third-parties/google in Next.js 14.2. GTM appears to intercept and process events before native handlers, causing significant performance degradation.

Performance Impact

• INP Score: Very high (failing Core Web Vitals)
• GTM Processing Time: ~90% of total interaction time
• Native Code: ~10% of total interaction time
• User Experience: Noticeable lag on simple interactions

Current Setup

// Next.js 14.2 with @next/third-parties/google
import { GoogleTagManager } from '@next/third-parties/google'

// In _app.js or layout
<GoogleTagManager gtmId="GTM-XXXXXX" />

our code looks like this

Simple anchor links for smooth scrolling to page sections:

<a
  key={index}
  href={`#h2_${index}`}
  style={{ display: 'block', margin: '10px 0' }}
  dangerouslySetInnerHTML={{
    __html: content.replace(/<[^>]+>/g, ''),
  }}
/>

Expected: Fast navigation to page sections
Actual: GTM processes the click event extensively before native scroll behavior

🔍 Investigation Results

Performance Panel Analysis

What We've Tried

❌ Attempt 1: preventDefault + requestAnimationFrame

onClick={(e) => {
  e.preventDefault();
  requestAnimationFrame(() => {
    document.getElementById(`h2_${index}`)?.scrollIntoView({
      behavior: 'smooth',
      block: 'start'
    });
  });
}}

Result: GTM still processes first, no performance improvement

---

📋 Environment Details

• Next.js: 14.2
• GTM Package: @next/third-parties/google

Looking forward to community insights and potential solutions!

---

Tags: #performance #core-web-vitals #gtm #analytics #next-third-parties

Additional information

No response

Example

No response

[aviraljain19]

@chandra2607 Did you find a solution? I’m having the same problem and have tried many fixes, but none of them worked.

[chandra2607]

hey @aviraljain19
we delayed GTM processing with the help of global script mentioned in this article.
In our case, GTM was triggering instantly after a user action, running before our own functions. We delayed the GTM trigger by approximately 200-250ms, which allowed our functions to execute first. For basic actions like a link or checkbox click, the INP score improved significantly.