What is definitelytyped?

fent/definitelytyped — explained in plain English

Analysis updated 2026-08-08 · repo last pushed 2019-10-29

★ 1Audience · developerComplexity · 2/5DormantLicenseSetup · easy

Mindmap

mindmap
  root((repo))
    What it does
      Type definitions
      Autocomplete support
      Error checking
    How it works
      npm install at-types
      Auto picked up
      No extra config
    Community
      Pull requests
      Maintainer reviews
      Auto publish to npm
    Quality control
      Automated checks
      Review bot
      Style guidelines
    Use cases
      Third-party libraries
      Editor autocomplete
      Safer TypeScript code
    Audience
      TypeScript developers
      Solo devs and teams
      Companies

mindmap root((repo)) What it does Type definitions Autocomplete support Error checking How it works npm install at-types Auto picked up No extra config Community Pull requests Maintainer reviews Auto publish to npm Quality control Automated checks Review bot Style guidelines Use cases Third-party libraries Editor autocomplete Safer TypeScript code Audience TypeScript developers Solo devs and teams Companies

What do people build with it?

USE CASE 1

Get autocomplete and error warnings when using a JavaScript library in a TypeScript project

USE CASE 2

Add missing type definitions for a library you use by submitting a pull request

USE CASE 3

Automatically install @types packages so your editor understands third-party library APIs

USE CASE 4

Remove outdated type packages when a library starts shipping its own built-in types

What is it built with?

TypeScriptnpmNode.js

How does it compare?

	fent/definitelytyped	0xallam/posthog	0xallam/search-engine
Stars	1	1	1
Language	—	Python	C++
Last pushed	2019-10-29	2026-03-26	2023-08-23
Maintenance	Dormant	Maintained	Dormant
Setup difficulty	easy	moderate	hard
Complexity	2/5	3/5	3/5
Audience	developer	pm founder	developer

Figures from each repo's GitHub metadata at analysis time.

How do you get it running?

Difficulty · easy Time to first run · 5min

Simply install the matching @types package via npm, no extra configuration needed.

Use freely for any purpose, including commercial use, as long as you keep the copyright notice.

So what is it?

TypeScript is a programming language that helps developers catch mistakes early by adding type information, details about what kind of data each piece of code expects. But many existing JavaScript libraries were built before TypeScript existed and don't include that type information. DefinitelyTyped solves this by providing a massive, community-maintained collection of type descriptions for thousands of popular libraries, so developers can use them in TypeScript projects with full safety and autocomplete support. If you're working in TypeScript and install a library like, say, a date formatting tool, your editor might not know what functions that tool exposes or what arguments they take. By installing the matching @types package from this project (for example, @types/node), your editor suddenly understands the library's API, showing you accurate autocomplete suggestions and warning you if you pass the wrong type of argument. The types are typically installed automatically and picked up by the TypeScript compiler with no extra configuration. This matters for anyone building software in TypeScript, whether you're a solo developer, a startup team, or a large company. If your project depends on third-party libraries (which most do), these type definitions make your development experience smoother and your code more reliable. The project runs entirely on community contributions: when someone notices a library is missing type definitions or has inaccurate ones, they can submit changes through a pull request. Maintainers review submissions, and approved packages are published to npm automatically, usually within minutes. The scale of this project is notable. It covers thousands of libraries and relies on hundreds of contributors, with automated systems checking quality and a bot helping coordinate reviews. The README also documents detailed style guidelines for contributors, for instance, discouraging overly vague types like Object or Function in favor of more specific ones. There's even a process for removing type packages when a library starts shipping its own built-in definitions, keeping things tidy and avoiding duplication.

Copy-paste prompts

Prompt 1

Install @types/node and show me how TypeScript now gives autocomplete for built-in Node.js functions like fs.readFile

Prompt 2

I'm using a date formatting library in TypeScript but getting no autocomplete, help me find and install the right @types package from DefinitelyTyped

Prompt 3

I want to contribute a type definition file for a JavaScript library that's missing from DefinitelyTyped, walk me through the folder structure and submission process

Prompt 4

Check my DefinitelyTyped type definition for overly vague types like Object or Function and suggest more specific replacements

Prompt 5

Help me understand when I should remove a @types package because the original library now ships its own built-in TypeScript definitions

Frequently asked questions