Installation

Effect Schema is included in the main effect package. There's no separate package to install.

Requirements

• TypeScript: 5.4 or higher
• Node.js: 18 or higher (for Node.js projects)
• strict mode: Must be enabled in tsconfig.json

Install Effect

npm

npm install effect

pnpm

pnpm add effect

yarn

yarn add effect

bun

bun add effect

TypeScript Configuration

Effect Schema requires TypeScript's strict mode. Ensure your tsconfig.json has:

{
  "compilerOptions": {
    "strict": true,
    // Recommended additional options
    "exactOptionalPropertyTypes": true,
    "moduleResolution": "bundler", // or "node16" / "nodenext"
    "module": "ESNext",
    "target": "ES2022"
  }
}

Why strict mode?

Schema's type inference relies on strict mode features like strictNullChecks and strictFunctionTypes. Without strict mode, types won't be inferred correctly and you'll encounter confusing type errors.

Importing Schema

Import Schema from the effect package:

import { Schema } from "effect"

// Now you can use Schema.String, Schema.Number, etc.
const mySchema = Schema.String

You can also import it with an alias if you prefer:

import { Schema as S } from "effect"

const mySchema = S.String

Verify Installation

Create a simple test file to verify everything works:

// test-schema.ts
import { Schema } from "effect"

const Person = Schema.Struct({
  name: Schema.String,
  age: Schema.Number
})

type Person = typeof Person.Type

const result = Schema.decodeUnknownSync(Person)({
  name: "Alice",
  age: 30
})

console.log(result)
// { name: 'Alice', age: 30 }

Run it:

npx tsx test-schema.ts

If you see the output { name: 'Alice', age: 30 }, you're all set!

Editor Setup

VS Code

For the best experience with Effect Schema in VS Code:

1. Use the TypeScript version from your workspace:

   • Press Cmd+Shift+P (Mac) or Ctrl+Shift+P (Windows/Linux)
   • Select "TypeScript: Select TypeScript Version"
   • Choose "Use Workspace Version"

2. Recommended extensions:

   • Error Lens - Inline error display
   • Pretty TypeScript Errors - Better error formatting

Other Editors

Schema works with any editor that supports TypeScript language services:

• WebStorm/IntelliJ: Works out of the box
• Neovim: Use with typescript-language-server
• Sublime Text: Use with LSP-typescript

Bundle Size

Effect is tree-shakeable. When using a modern bundler (Vite, esbuild, Rollup, webpack 5+), only the parts you use are included in your bundle.

A minimal Schema usage typically adds ~10-15KB (minified + gzipped) to your bundle.

Using with Different Module Systems

ESM (Recommended)

Effect is distributed as ESM. Modern bundlers and Node.js 18+ handle this natively:

import { Schema } from "effect"

CommonJS

If you're in a CommonJS environment, you may need to use dynamic import:

const { Schema } = await import("effect")

Or configure your bundler to handle ESM modules.

Next Steps

Now that Schema is installed, let's write your first schema:

→ Quick Start