SEO

How to Improve SEO in Next.js with Smarter Script Management

Blazity team

23 Jun 2025

•

2 min. read

How to Improve SEO in Next.js with Smarter Script Management

Introduction to Script Loading and its Impact on Web Performance

Script loading is critical to web development because it directly affects website performance, influencing user experience and SEO.

Impact on the Main Thread

The main thread parses HTML, executes JavaScript, and renders page content. Since JavaScript is inherently blocking, the browser must pause other tasks until the script is downloaded and executed.

Script Loading Strategies to Mitigate Blocking

<script> in <head>: Highly critical scripts
<link rel="preload"> + <script async>: Medium to high priority scripts
<script async>: Non-critical scripts
<script defer>: Low priority scripts
<script> at end of <body>: Lowest priority scripts

How to Implement Script Loading?

Next.js provides the next/script component to simplify and optimize script handling.

beforeInteractive

For scripts that must run before the page becomes interactive. Scripts are embedded directly into server-rendered HTML.

import Script from 'next/script';

<Script
  strategy="beforeInteractive"
  src="/path/to/bot-detector.js"
/>

Use Cases: Critical third-party integrations (Stripe, PayPal), security measures (CSP).

afterInteractive

Loads scripts right after the page becomes interactive. Injected on the client side after hydration.

import Script from 'next/script';

<Script
  strategy="afterInteractive"
  src="https://www.googletagmanager.com/gtag/js?id=GA_MEASUREMENT_ID"
/>

Use Cases: Analytics (Google Analytics, Facebook Pixel), live chat (Intercom, Drift), feedback tools (Hotjar).

lazyOnLoad

Loaded during browser's idle time using requestIdleCallback.

import Script from 'next/script';

<Script
  strategy="lazyOnload"
  src="/path/to/social-media-widget.js"
/>

Use Cases: Social media widgets, ad scripts, additional multimedia content.

Enhancing Script Management with Callback Functions

onLoad: Executes when the script has successfully loaded.
onReady: Ensures the script is fully loaded and ready to execute.
onError: Executes if the script fails to load.

Next-third-parties

The @next/third-parties library simplifies integrating popular third-party scripts:

import { GoogleTagManager, GoogleAnalytics } from "@next/third-parties/google";
import { YouTubeEmbed } from "@next/third-parties/youtube";

Keypoints

next/Script simplifies adding and managing scripts in Next.js.
beforeInteractive loads scripts before the page becomes interactive.
afterInteractive loads scripts after the page becomes interactive.
lazyOnload loads scripts in the background after the page fully loads.
Support for external scripts enables seamless integration of analytics, ads, and third-party tools.
Optimized script handling improves Core Web Vitals, boosting SEO.

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