By the numbers

Data collected on 2026-04-30 against commit 4ba05cc300cd3f196bdcebe56de2f6811171bb68 on the canary branch.

Size

The repository is dual-language: TypeScript/JavaScript for the framework runtime and CLI, Rust for the compiler and bundler.

xychart-beta horizontal
    title "Lines of source code by area"
    x-axis ["TypeScript (packages/next/src)", "Rust (crates/ + turbopack/crates)", "MDX docs", "JavaScript (packages)"]
    y-axis "Lines of code" 0 --> 280000
    bar [273149, 269139, 71035, 11389]

Area	Lines	Files
TypeScript in packages/next/src/	273,149	1,592
Rust in crates/ + turbopack/crates/	269,139	948
Documentation (MDX) in docs/	71,035	many
JavaScript in packages/ (excl. compiled)	11,389	many

Other counts	Value
Total git commits (since 2016-10-05)	33,861
Cargo workspace Cargo.toml files	69
Vendored compiled packages in packages/next/src/compiled/	141
Example apps in examples/	229
Test files	1,714

The flagship packages/next package has 1,592 TypeScript files and a 273k-line src/ tree. The Rust side is comparably sized at 269k lines split across 948 files in 69 Cargo crates.

Activity

The project moves quickly. Recent commit volume is sustained at thousands of commits per quarter.

Window	Commits
Last 90 days	1,325
Last 6 months	2,330
Total	33,861

Most-changed top-level paths in the last 90 days

Path	Touches
packages/next/	3,965
turbopack/crates/	3,835
test/e2e/	2,332
docs/01-app/	359
test/production/	339
test/development/	314
crates/next-core/	261
evals/evals/	203
test/integration/	182
packages/create-next-app/	179
packages/next-routing/	173

The packages/next core, the Turbopack subtree, and the e2e test suite together account for the majority of activity.

Bot-attributed commits

Of the 2,330 commits in the last 6 months:

• 41 commits with [bot] in the subject line (≈1.8%)
• 51 commits with [bot] in the Co-authored-by: trailer (≈2.2%)

These numbers are a lower bound — they only count commits that explicitly attribute work to a bot. Commits made with inline AI assistance (Copilot, Cursor, ChatGPT) leave no trace in git history.

Complexity

Largest source files

The biggest files are the App Router renderer, the build orchestrator, and the segment cache.

File	Lines	Why it's big
packages/next/src/server/app-render/app-render.tsx	8,759	The App Router renderer — RSC + SSR + PPR pipeline
packages/next/src/build/index.ts	4,401	Build pipeline orchestration
packages/next/src/client/components/segment-cache/cache.ts	3,112	Client-side segment cache
packages/next/src/server/base-server.ts	3,070	Shared server logic for Node + Edge
packages/next/src/build/webpack-config.ts	2,936	webpack config generator
packages/next/src/server/use-cache/use-cache-wrapper.ts	2,861	The 'use cache' directive runtime
packages/next/src/shared/lib/router/router.ts	2,630	Pages Router state machine
packages/next/src/server/config.ts	2,321	Config loader and validator
packages/next/src/build/adapter/build-complete.ts	2,215	Adapter for hosting platforms
packages/next/src/server/config-shared.ts	2,201	Config types and defaults
packages/next/src/server/next-server.ts	2,178	Node.js production server
packages/next/src/client/components/router-reducer/ppr-navigations.ts	2,061	PPR navigation reducer
packages/next/src/build/templates/app-page.ts	2,028	Template compiled into user bundles

TODO / FIXME / HACK comments

packages/next/src/ contains 729 lines tagged TODO, FIXME, or HACK. Many are scoped to specific features (cache components migration, Turbopack parity gaps) and turn over with releases.

Dependency surface

The root package.json lists ~270 lines of dependencies (devDependencies plus pinned overrides). The framework itself bundles 141 third-party packages into packages/next/src/compiled/ so users do not transitively pull them in. Notable inclusions: webpack 5, postcss, browserslist, busboy, async-sema, the @opentelemetry/* family, and the entire Babel toolchain.

Per-area pulse

Area	Source files	Tests	Recent activity (90d)
App Router runtime	packages/next/src/server/app-render/ (~70 files)	test/e2e/app-dir/ (1000+ tests)	very high
Pages Router	packages/next/src/server/render.tsx, pages/	test/integration/	moderate
Build pipeline	packages/next/src/build/ (~150 files)	test/production/	high
Dev server	packages/next/src/server/dev/ (~22 files)	test/development/	high
Turbopack	turbopack/crates/ (54 crates)	turbopack/crates/turbopack-tests/	very high
next-swc	crates/next-custom-transforms/	fixture-based	moderate

For per-subsystem dives, see the systems, packages, crates, and turbopack sections.