TSConfig

lib

TypeScript includes a default set of type definitions for built-in JS APIs (like Math), as well as type definitions for things found in browser environments (like document). TypeScript also includes APIs for newer JS features matching the target you specify; for example the definition for Map is available if target is ES6 or newer.

You may want to change these for a few reasons:

  • Your program doesn’t run in a browser, so you don’t want the "dom" type definitions
  • Your runtime platform provides certain JavaScript API objects (maybe through polyfills), but doesn’t yet support the full syntax of a given ECMAScript version
  • You have polyfills or native implementations for some, but not all, of a higher level ECMAScript version

In TypeScript 4.5, lib files can be overriden by npm modules, find out more in the blog.

High Level libraries

Name Contents
ES5 Core definitions for all ES3 and ES5 functionality
ES2015 Additional APIs available in ES2015 (also known as ES6) - array.find, Promise, Proxy, Symbol, Map, Set, Reflect, etc.
ES6 Alias for “ES2015”
ES2016 Additional APIs available in ES2016 - array.include, etc.
ES7 Alias for “ES2016”
ES2017 Additional APIs available in ES2017 - Object.entries, Object.values, Atomics, SharedArrayBuffer, date.formatToParts, typed arrays, etc.
ES2018 Additional APIs available in ES2018 - async iterables, promise.finally, Intl.PluralRules, regexp.groups, etc.
ES2019 Additional APIs available in ES2019 - array.flat, array.flatMap, Object.fromEntries, string.trimStart, string.trimEnd, etc.
ES2020 Additional APIs available in ES2020 - string.matchAll, etc.
ES2021 Additional APIs available in ES2021 - promise.any, string.replaceAll etc.
ESNext Additional APIs available in ESNext - This changes as the JavaScript specification evolves
DOM DOM definitions - window, document, etc.
WebWorker APIs available in WebWorker contexts
ScriptHost APIs for the Windows Script Hosting System

Individual library components

Name
DOM.Iterable
ES2015.Core
ES2015.Collection
ES2015.Generator
ES2015.Iterable
ES2015.Promise
ES2015.Proxy
ES2015.Reflect
ES2015.Symbol
ES2015.Symbol.WellKnown
ES2016.Array.Include
ES2017.object
ES2017.Intl
ES2017.SharedMemory
ES2017.String
ES2017.TypedArrays
ES2018.Intl
ES2018.Promise
ES2018.RegExp
ES2019.Array
ES2019.Object
ES2019.String
ES2019.Symbol
ES2020.String
ES2020.Symbol.wellknown
ES2021.Promise
ES2021.String
ES2021.Weakref
ESNext.AsyncIterable
ESNext.Array
ESNext.Intl
ESNext.Symbol

This list may be out of date, you can see the full list in the TypeScript source code.