What is the TypeScript project references feature?

Project references (TypeScript 3.0) allow you to split a large TypeScript codebase into smaller, independently compilable projects. Each sub-project has its own tsconfig.json with "composite": true and declares its dependencies on other sub-projects via "references". Building with tsc --build (or tsc -b) compiles each sub-project in dependency order and only recompiles what changed. Benefits: (1) Faster builds — only changed projects and their dependents recompile, not the entire codebase. (2) Logical separation — clear package boundaries and dependency graph. (3) Independent versioning — each project can have its own tsconfig settings. (4) Better IDE performance — editors can load only relevant parts of a large codebase. Configure: the root tsconfig references sub-projects, each sub-project has "composite": true and "declarationDir" set. Project references are essential for monorepos and large enterprise TypeScript applications.