Effect

[](https://pkg.pr.new/~/Effect-TS/effect)

# Effect

Effect is a library for building robust, maintainable, type-safe, and production grade applications in TypeScript. It helps you handle the hard problems at scale: typed errors, dependency injection, structured concurrency, scheduling, tracing, and unified schema validation.

> **Effect V4 is currently a release candidate.** The `main` branch contains v4 development.

## Install V4 RC

```sh
npm install effect@rc
```

## Requirements

- **TypeScript 5.9 or newer.** TypeScript 7 is recommended for the best performance and compatibility with [Effect's TypeScript tooling](https://github.com/Effect-TS/tsgo#installation).
- **Node.js 18 or newer** is the general minimum for running Effect on Node.js. Some integration packages require newer runtimes; for example, `@effect/sql-sqlite-node` requires Node.js 22.16 or newer.
- **Strict type-checking:** the `strict` flag must be enabled in your `tsconfig.json`.

## Effect v3

The Effect v3 source code is available on the [`v3`](https://github.com/Effect-TS/effect/tree/v3) branch, which is also where issues and pull requests meant for Effect v3 should be targeted.

## Packages

This monorepo contains the core `effect` package alongside integration packages that extend it. All v4 packages are published under the `rc` tag on npm.

| Package                                                               | Description                                              | API Reference                                                      |
| --------------------------------------------------------------------- | -------------------------------------------------------- | ------------------------------------------------------------------ |
| [`effect`](packages/effect)