By default all visible "@types" packages are included in your compilation. Packages in node_modules/@types of any enclosing folder are considered visible. For example, that means packages within ./node_modules/@types/, ../node_modules/@types/, ../../node_modules/@types/, and so on.

If types is specified, only packages listed will be included in the global scope. For instance:

{
  "compilerOptions": {
    "types": ["node", "jest", "express"]
  }
}

{
  "compilerOptions": {
    "types": ["node", "jest", "express"]
  }
}

This tsconfig.json file will only include ./node_modules/@types/node, ./node_modules/@types/jest and ./node_modules/@types/express. Other packages under node_modules/@types/* will not be included.

What does this affect? ​

This option does not affect how @types/* are included in your application code, for example if you had the above compilerOptions example with code like:

import * as moment from "moment";

moment().format("MMMM Do YYYY, h:mm:ss a");

import * as moment from "moment";

moment().format("MMMM Do YYYY, h:mm:ss a");

The moment import would be fully typed.

When you have this option set, by not including a module in the types array it:

• Will not add globals to your project (e.g process in node, or expect in Jest)
• Will not have exports appear as auto-import recommendations

This feature differs from typeRoots in that it is about specifying only the exact types you want included, whereas typeRoots supports saying you want particular folders.