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TypeScript Monorepo Project

A larger TypeScript monorepo can contain applications and shared packages with clear dependency boundaries. Project references and workspace tooling support this structure.

In this page:

  1. Core Concept
  2. Basic Setup
  3. Typed Example
  4. Project Usage
  5. Best Practices

Core Concept

A full monorepo project applies everything a smaller TypeScript setup uses — project references, a shared-types package, workspace tooling — at the scale of a real multi-package application with a build pipeline tying it together.

Example: Core Concept

typescript 
// packages/api (references packages/shared)
// packages/web (references packages/shared)
console.log("Project references + shared-types + workspace tooling combined");

Basic Setup

A basic setup wires workspace packages (via npm/yarn/pnpm workspaces) with each package's tsconfig.json referencing its dependencies, and a root build script (often Turborepo or Nx) orchestrating builds in dependency order.

Example: Basic Setup

typescript 
// root: { "workspaces": ["packages/*"] }
// turbo.json orchestrates builds across packages in dependency order
console.log("Turborepo/Nx build packages in the correct dependency order");

Typed Example

A typed example: a packages/api package exports typed route handlers, packages/web imports typed API-response shapes from packages/shared, and both build against the same TypeScript version enforced at the workspace root.

Example: Typed Example

typescript 
// packages/shared/index.ts
export interface ApiUser { id: number; name: string; }
// packages/web imports ApiUser from packages/shared
const user: import("./shared").ApiUser = { id: 1, name: "Ravi" } as any;
console.log("packages/api and packages/web share one TypeScript version");

Project Usage

In a real project, build caching (Turborepo/Nx skip rebuilding packages whose inputs haven't changed) is what keeps a large monorepo's CI fast even as the number of packages grows into the dozens.

Example: Project Usage

typescript 
// turbo run build --filter=...changed
console.log("Build caching skips rebuilding packages with unchanged inputs");

Best Practices

Pin a single TypeScript version at the workspace root rather than letting each package specify its own, since mismatched compiler versions across packages in one monorepo are a frequent, hard-to-diagnose source of subtly different type-checking behavior.

Example: Best Practices

typescript 
// root package.json: { "devDependencies": { "typescript": "5.4.0" } }
// individual packages should NOT pin their own separate typescript version.
console.log("Pin one TypeScript version at the workspace root");
Related Topics

Monorepo Setup · TypeScript Project References · Project References · Setting Up React TypeScript Project

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Common Mistakes
  1. Forgetting to add project references or workspace links, so a package cannot see its sibling's types.
  2. Building packages in the wrong order so dependents use missing or stale output.
  3. Putting the same dependency at different versions in each package, causing type mismatches.
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