Effect is a library for building robust, maintainable, type-safe, and production grade applications in TypeScript.
The effect package is the core of the framework. It provides primitives for managing side effects, errors, concurrency, resources, and structured data, alongside a rich standard library.
npm install effect@rc-
TypeScript 5.9 or newer. TypeScript 7 is recommended for the best performance and compatibility with Effect's TypeScript tooling.
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Node.js 18 or newer when running Effect on Node.js.
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Strict type-checking: the
strictflag must be enabled in yourtsconfig.json:{ "compilerOptions": { "strict": true } }
The effect package is a collection of modules. Some of the core ones:
| Module | Description |
|---|---|
| Effect | The core abstraction for managing side effects, concurrency, and error handling in a structured way. |
| Context | A lightweight dependency injection mechanism that enables passing services through computations without direct references. |
| Layer | A system for managing dependencies, allowing for modular and composable resource allocation. |
| Fiber | Lightweight virtual threads with resource-safe cancellation capabilities, enabling many features in Effect. |
| Stream | A powerful abstraction for handling asynchronous, event-driven data processing. |
| Schedule | A module for defining retry and repeat policies with composable schedules. |
| Scope | Manages the lifecycle of resources, ensuring proper acquisition and release. |
| Schema | A powerful library for defining, validating, and transforming structured data with type-safe encoding and decoding. |
In v4, functionality that previously lived in separate packages ships inside effect under the effect/unstable/* namespaces, including http, httpapi, rpc, cluster, workflow, cli, ai, sql, and reactivity.