Route prefetching behavior in NextJS - Step-by-Step Execution

Concept Flow - Route prefetching behavior

Page loads

↓

Next.js scans <Link> components

↓

Prefetch triggered for linked routes

↓

Browser downloads JS bundles for prefetched routes

↓

Prefetched data cached

↓

User clicks link

↓

Route loads instantly from cache

↓

Page rendered quickly

↓

Prefetch for other links continues

↓

Repeat for new links

Next.js automatically prefetches linked routes after page load to speed up navigation by downloading code in advance.

Execution Sample

NextJS

import Link from 'next/link';

export default function Home() {
  return <Link href="/about">About</Link>;
}

This code renders a link to the /about page which Next.js will prefetch automatically after the Home page loads.

Execution Table

Step	Action	Prefetch Triggered?	Prefetched Route	Cache State	User Interaction	Page Load Result
1	Home page loads	No	None	Empty	No	Home page rendered
2	Next.js scans <Link> to /about	Yes	/about	Prefetching /about started	No	Home page rendered
3	Browser downloads /about JS bundles	Yes	/about	Cached /about bundles	No	Home page rendered
4	User clicks /about link	No	/about	Cached /about bundles	Yes	/about page loads instantly
5	Next.js scans new links on /about	Yes	Other linked routes	Prefetching new routes	No	/about page rendered
6	User clicks another link	No	Cached route	Cached bundles	Yes	New page loads instantly

💡 Prefetching stops when user navigates away or all linked routes are cached.

Variable Tracker

Variable	Start	After Step 2	After Step 3	After Step 4	After Step 5	Final
Prefetch Triggered?	No	Yes	Yes	No	Yes	No
Prefetched Route	None	/about	/about	/about	Other linked routes	Cached route
Cache State	Empty	Prefetching /about started	Cached /about bundles	Cached /about bundles	Prefetching new routes	Cached bundles
User Interaction	No	No	No	Yes	No	Yes
Page Load Result	Home page rendered	Home page rendered	Home page rendered	/about page loads instantly	/about page rendered	New page loads instantly

Key Moments - 3 Insights

Why does Next.js prefetch routes even before the user clicks the link?

Next.js prefetches linked routes after the page loads to make navigation faster by having the code ready in cache, as shown in execution_table step 2 and 3.

Does prefetching happen again after the user navigates to a new page?

Yes, Next.js scans new links on the new page and prefetches those routes, as seen in step 5 of the execution_table.

What happens if the user clicks a link before prefetching finishes?

The route will load normally but might be slower because the bundles are not cached yet; prefetching aims to avoid this delay by starting early.

Visual Quiz - 3 Questions

Look at the execution_table, at which step does the /about page bundles get cached?

A Step 2

B Step 3

C Step 4

D Step 5

💡 Hint

Check the 'Cache State' column in execution_table rows.

According to variable_tracker, what is the 'User Interaction' value after step 4?

A Yes

B No

C Maybe

D Unknown

💡 Hint

Look at the 'User Interaction' row and the 'After Step 4' column.

If the Home page had no <Link> components, how would the prefetch behavior change?

A Prefetching would still happen for /about

B Prefetching would happen for all routes

C No prefetching would occur

D Prefetching would happen only after user clicks

💡 Hint

Prefetching depends on scanning components as shown in concept_flow.

Concept Snapshot

Next.js Route Prefetching:
- Automatically prefetches linked routes after page load
- Downloads JS bundles in background
- Caches bundles for instant navigation
- Prefetch repeats on new pages
- Speeds up user experience by reducing wait time

Full Transcript

When a Next.js page loads, it looks for <Link> components on the page. For each link, Next.js starts prefetching the JavaScript bundles needed for that route in the background. This means the code is downloaded and cached before the user clicks the link. When the user clicks, the page loads instantly from cache, making navigation very fast. After navigating, Next.js repeats this process for new links on the new page. If there are no links, no prefetching happens. This behavior improves user experience by reducing wait times during navigation.