Module Resolution
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What Module Resolution Does
When TypeScript sees an import statement, it needs to locate the actual file or package being referenced — module resolution is the set of rules that determines exactly how and where it looks.
Example: What Module Resolution Does
// import { helper } from "./utils";
// TypeScript must locate the actual utils.ts/.d.ts file this refers to.
console.log("Module resolution determines how imports map to real files");Node10 Resolution
Node10 resolution follows the traditional Node.js package and file lookup behavior, and is commonly associated with older CommonJS-style projects that predate the package.json exports field.
Example: Node10 Resolution
// tsconfig.json
// { "compilerOptions": { "moduleResolution": "node10" } }
console.log("Node10 follows traditional CommonJS-style lookup rules");Node16 and NodeNext
Node16 and NodeNext model modern Node.js module behavior more precisely, including package.json metadata and the real distinction between CommonJS and ES modules, which older resolution modes don't understand.
Example: Node16 and NodeNext
// tsconfig.json
// { "compilerOptions": { "moduleResolution": "nodenext" } }
console.log("NodeNext models modern Node's package.json exports and ESM/CJS split");Bundler Resolution
Bundler resolution is designed for projects where a tool like webpack or Vite handles module loading — it supports package exports and bundler-specific conventions without assuming Node's runtime resolution rules apply.
Example: Bundler Resolution
// tsconfig.json
// { "compilerOptions": { "moduleResolution": "bundler" } }
console.log("Bundler resolution suits projects using webpack/Vite for loading");Tracing Resolution
The traceResolution compiler flag can print exactly which paths TypeScript tried and why a module lookup succeeded or failed, which is invaluable when debugging a mysterious "cannot find module" error.
Example: Tracing Resolution
// tsc --traceResolution
console.log("traceResolution prints exactly which paths were tried and why");Chapter Quiz — Complete all 7 topics to unlock
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