What is incremental compilation in TypeScript

Short answer

Incremental compilation saves a summary of the last compilation to a .tsbuildinfo file, allowing TypeScript to skip re-checking unchanged files on subsequent runs.

How it works

When incremental: true is set, TypeScript writes build metadata including file hashes and dependency graphs. On the next invocation, it reads this file to determine what has changed and only re-emits affected outputs. This is especially effective for large codebases.

Example

{
  "compilerOptions": {
    "incremental": true,
    "tsBuildInfoFile": "./.tsbuildinfo"
  }
}

Why it matters

Without incremental builds, every tsc invocation re-checks the entire project. Incremental mode reduces feedback loops during development and CI, especially when combined with project references.