Khoury College of Computer Sciences
CS 4550 / CS 5610 · Web Development · Fall 2026
Turbopack chunking: fewer requests without over-shipping JS
- Next.js
- Course
Instructor-curated digest, not original reporting. Each post paraphrases a public article and links to the original source.
On September 3, 2026, Next.js explained how Turbopack decides which code goes in which JavaScript file. One big chunk earns cache hits but over-ships; one chunk per page duplicates shared code; one chunk per module creates too many requests. Turbopack merges smaller chunks within a chunk group, the chunks loaded together for a route.
On nextjs.org demo navigations, no merging was 561.6 KiB and 96 requests, Turbopack defaults were 554.8 KiB and 38 requests, and one chunk per group was 610.0 KiB and 15 requests. In Next.js 16.3, experimental.turbopackChunking.generateComponentChunks emits un-merged versions so the runtime can load only the missing pieces on soft navigations. The same experimental.turbopackChunking options include firstPageLoadPriority, priorityRoutes, and clusters. experimental.turbopackCjsTreeShaking covers CommonJS tree-shaking, and experimental.turbopackSharedRuntime saves about 10 KB after the first navigation.
That chunking is part of the App Router and Next.js tooling in Chapter 1.
Read original: How Turbopack chunks your JavaScript — Next.js
Related in the book: Chapter 1