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8.0.7 • Public • Published



Higher Type Safety for TypeScript. A collection of useful types.

Language grade: JavaScript

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📖 Read Docs · 🎮 View Demo · 🐞 Report Bug · 🍩 Request Feature · 🤔 Ask Questions

Table of Contents

📜 About

"Avoid bugs by writing high quality types"

ts-toolbelt ships utility types that provide simple ways to update, change, and compute TypeScript types. It offers unique dynamic features, allowing you to write type-safe software more easily and in less time than you do today.

Its programmatic API brings new capabilities to TypeScript with +200 tested type utilities. This makes it the largest and the most reliable type collection out there. It uses the type system itself for TypeScript to compute complex types. So its API exposes types that trade CPU & RAM for higher type safety.


  • Answer the question to "How can I do this in TypeScript?"
  • Provide a programmatic standard API for the type system
  • Promote type evolution/reusability within your codebase
  • Software that is more type-safe, flexible, and robust
  • Bring a whole new set of extra features to TypeScript
  • Extensively tested type utilities for maximum type safety
  • This package aims to be the home of all utility types
  • Answer questions about types and share knowledge

You'll find all the types you can ever need in this single and well organized package.

🍩 Features

Here's some of the most useful utilities:

TIP If you don't find the type you are looking for, you are welcome to open a feature request!

🏁 Getting Started


Lowest TypeScript support starts at v3.5

npm install typescript@^3.8.0 --save-dev

For best results, add this to your tsconfig.json

    // highly recommended (required by few utilities)
    // this is optional, but enable whenever possible
    // this is the lowest supported standard library


npm install ts-toolbelt --save

Hello World

import {Object} from "ts-toolbelt"
// Check the docs below for more
// Merge two `object` together
type merge = Object.Merge<{name: string}, {age?: number}>
// {name: string, age?: number}
// Make a field of an `object` optional
type optional = Object.Optional<{id: number, name: string}, "name"}>
// {id: number, name?: string}

TIP You can also grab the demo over here.

You can level-up, and re-code this library from scratch.

📖 Documentation ⤢

Where to start

To get you started, we recommend that you visit the documentation of the following essential tools.

Object List Function Any Union
Either Append NoInfer Compute Filter
Exclude Concat Parameters Promisable IntersectOf
Filter Drop Promisify Type Merge
Merge Flatten Return Select
NonNullable Pop Strict
Nullable Prepend
Omit Remove
Optional Reverse
Overwrite Tail

TIP Add something to this list

The documentation is complete but it needs more examples. So feel free to ask for examples.


The project is organized around TypeScript's main concepts:

Any Boolean Class Function Iteration List
Number Object Object.P String Union Test

TIP How to choose categories? Match your type with them.

There are many ways to import the types into your project:

  • Explicit

    import {Any, Boolean, Class, Function, Iteration, List, Number, Object, String, Union} from "ts-toolbelt"
  • Compact

    import {A, B, C, F, I, L, N, O, S, U} from "ts-toolbelt"
  • Portable

    import tb from "ts-toolbelt"

You can also import our non-official API from the community:

import {Community} from "ts-toolbelt"

TIP The community API is for our community to publish useful types that don't see fit in the standard API.

Internal Docs

If you're interested to learn how the internals work, this tutorial will get you on track to start writing your own types.

Archives ⤢

Access older docs at


🧠 Good to Know ⤢

In this wiki, you will find some extra resources for your learning, and understanding.

Are you missing something? Participate to the open-wiki by posting your questions.

📣 Announcements ⤢

Stay up to date with the latest announcements with this regular digest of important changes.

🎁 Contributing

Contributions are what make the open source community such an amazing place to learn, inspire, and create. Any contributions you make are greatly appreciated. There are many ways to contribute to the project:



Pull Requests

  1. Read the tutorial

  2. Fork the project

  3. Clone your fork

  4. Create a pr/feature branch

    git checkout -b pr/CoolFeature
  5. Commit your changes

    You must follow the conventional commit to be able to commit

    git commit -m "feat(name): Added this CoolFeature"
  6. Run the tests

  7. Push your changes

    npm run release -- --no-tags
  8. Open a pull request

💉 Running tests

For this project

To run the lint & type tests, simply run:

npm test

For your project

Want to test your own types? Let's get started:

import {Number, Test} from "ts-toolbelt"
const {checks, check} = Test
    check<Number.Plus<"1", "30">, "31", Test.Pass>(),
    check<Number.Plus<"5", "-3">, "2",  Test.Pass>(),

TIP Place it in a file that won't be executed, it's just for TypeScript to test types.

Continuous Integration

The releases are done with Travis CI in stages & whenever a branch or PR is pushed:

  • Tests are run with npm test
  • Tests against DefinitelyTyped
  • Releases to npm@[branch-name]

If you wrote tests & would like your project to be tested too, please open an issue.

🔧 Compatibility

The project is maintained to adapt to the constant changes of TypeScript:

ts-toolbelt typescript
8.x.x ^4.0.x
6.x.x ^3.7.x
4.x.x ^3.5.x
2.x.x ^3.5.x
3.x.x ^3.5.x
1.x.x ~3.5.x

Major version numbers will upgrade whenever TypeScript had breaking changes (it happened that TS had breaking changes on minor versions). Otherwise, the release versions will naturally follow the semantic versioning.

👏 Sponsoring issues

Sponsored issues have higher priority over non-critical issues.

You can either request a new feature or a bug fix, and then fund it.

The money will be transparently split with an issue's assignees.

🔮 What's next

  • Automated performance tests

    # performance is checked manually with  
    npx tsc --noEmit --extendedDiagnostics
  • Need to write more examples

🙏 Acknowledgements

Many, many thanks to all the contributors and:

💟 Friendly Projects

  • eledoc - 🌒 A material dark theme for TypeDoc
  • utility-types - Collection of utility types, complementing TypeScript built-in mapped types and aliases


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