Effect

TypeScript library for typed errors, concurrency, and resource-safe programs, now at version 4

Abouteffect.website

Effect is a TypeScript library for building complex synchronous and asynchronous programs with typed errors, concurrency, and resource safety. Effect 4.0 unifies the ecosystem with zero dependencies. It has docs, a playground, a podcast, and a language service for editors.

Install

npm install effect

For an agent

Use it for complex app logic where errors must be explicit. Budget learning time, because the style differs from plain TypeScript.

Why it is here. It is a leading library for reliable TypeScript programs.

Install command, framework, licence and component list.

Notable for

Typed errors
Effect 4.0
Zero dependencies

Provenance

Verified 2026-10-09. HTTP 200. https://effect.website/ (HTTP 200, page fetched 2026-10-09), https://github.com/Effect-TS/effect (GitHub API, 17174 stars), depo.zip listing https://www.depo.zip/tools/j57b48njbf4cm1r9j9tpp5k6yh7t6dq6

Utilities & Naming