Fantasy Land vs fp-ts
Which should you use? A side-by-side look at what each one does, who it suits, what it costs, how hard it is to set up, and where each falls short.
Open source · MIT
A written specification so JavaScript data types can work together through shared method names and laws.
Open source · MIT
A TypeScript library bringing common functional programming types like Option and Either.
The short answer
Choose Fantasy Land if you need…
- JavaScript developers who write or use functional-style data types
- Library authors who want their types to interoperate with other functional libraries
- Developers learning the vocabulary of algebraic structures like functors and monads
- Teams evaluating whether a library follows a common interoperability standard
Choose fp-ts if you need…
- Developers already familiar with functional programming who want these patterns in TypeScript
- Teams using TypeScript with strict mode enabled, which the library is designed for
- Projects that need typed abstractions like Option and Either for error handling
- Developers maintaining existing codebases that already depend on fp-ts
Side-by-side
| Fantasy Land | fp-ts | |
|---|---|---|
| Type | Learning resource | Library |
| Price | Free and open source | Free and open source |
| Licence | MIT | MIT |
| GitHub stars | 10.2k | 11.5k |
| Setup difficulty | Advanced | Intermediate |
| How you get it | Read it online | Install with a package manager |
| Main language | JavaScript | TypeScript |
| Last code update | 24 months ago | 7 months ago |
What each one is
Fantasy Land
Fantasy Land is a specification, not a library you run. It defines standard method names and laws (such as Functor, Monoid, and Monad) that algebraic data types in JavaScript should follow, so that separate libraries can swap values safely. The README describes a family of these algebras and how they depend on each other.
fp-ts
fp-ts is a TypeScript library that provides common functional programming building blocks, such as Option, Either, IO, Task, and abstractions like Functor, Applicative, and Monad. It is aimed at developers who want to write code in a functional style with strong type checking. The README notes that it implements Higher Kinded Types, which TypeScript does not support natively. The README also announces that fp-ts is merging into the Effect-TS ecosystem, which it describes as the successor to fp-ts v2.
Best for
Fantasy Land
- JavaScript developers who write or use functional-style data types
- Library authors who want their types to interoperate with other functional libraries
- Developers learning the vocabulary of algebraic structures like functors and monads
- Teams evaluating whether a library follows a common interoperability standard
fp-ts
- Developers already familiar with functional programming who want these patterns in TypeScript
- Teams using TypeScript with strict mode enabled, which the library is designed for
- Projects that need typed abstractions like Option and Either for error handling
- Developers maintaining existing codebases that already depend on fp-ts
Strengths
Fantasy Land
- Gives a shared vocabulary and set of method names across functional JavaScript libraries
- Explains terms like equivalence and type signature notation clearly in the README
- Released under the permissive MIT license
fp-ts
- Includes widely used types and abstractions modeled on Haskell, PureScript, and Scala
- Implements Higher Kinded Types, a feature TypeScript lacks natively
- Documented API reference, learning resources, and an ecosystem page
Not ideal for
Fantasy Land
- Developers who only need to build ordinary web pages, since the spec does not provide UI or app tooling
- Beginners with no interest in functional programming, because the README assumes familiarity with these algebraic concepts
- Anyone expecting an installable package, because the README describes laws rather than code to install
fp-ts
- Beginners learning functional programming, because the docs assume you already know FP concepts
- New projects that want the newest direction, since the README points users to Effect-TS as the successor to fp-ts v2
- Projects using TypeScript older than 3.5, since version 2.0.x requires TypeScript 3.5 or newer
Trade-offs
Fantasy Land
- It is a specification, so it does not ship runnable features on its own
- The README excerpt is truncated, so full details of each algebra are not visible here
- Assumes a background in algebraic structures and type theory
fp-ts
- The README announces a merge into Effect-TS, so the long-term direction of this project is changing
- Teaching functional programming is out of scope, so beginners will need outside resources
- Multiple installed versions can cause tsc to hang, so dependency management needs care
Getting started
Fantasy Land
Clone the repository
git clone https://github.com/fantasyland/fantasy-landfp-ts
Install the stable version
npm install fp-tsCheck installed versions
npm ls fp-tsFrequently asked questions
What is the difference between Fantasy Land and fp-ts?
Fantasy Land: A written specification so JavaScript data types can work together through shared method names and laws. fp-ts: A TypeScript library bringing common functional programming types like Option and Either. Fantasy Land suits javascript developers who write or use functional-style data types, while fp-ts suits developers already familiar with functional programming who want these patterns in typescript.
Are Fantasy Land and fp-ts free?
Fantasy Land: Free and open source. fp-ts: Free and open source.
Which is easier to set up, Fantasy Land or fp-ts?
fp-ts is easier to get started with (rated intermediate); Fantasy Land is rated advanced and usually needs more setup.
Is Fantasy Land or fp-ts more popular?
fp-ts has more GitHub stars (11.5k) than Fantasy Land (10.2k). Popularity isn't the same as fit — check which one matches your use case above.
What are other alternatives to Fantasy Land and fp-ts?
Other options people compare them with include Ramda, Effect.
Keep comparing
Built from our catalogue entries for both products: open-source details come from each project's README (AI-assisted, refreshed weekly) and GitHub data; AI-tool details are editorial. Spotted something wrong? Let us know from either product's page.