Quick Start: run Elysia on Bun or Node.js

Elysia is a TypeScript backend framework with support for multiple runtimes, optimized for Bun. The steps below walk you through getting a running server regardless of which runtime you are targeting.

Bun
Node.js
Web Standard

Install Bun

Elysia is optimized for Bun, a fast JavaScript runtime designed as a drop-in replacement for Node.js.

curl -fsSL https://bun.sh/install | bash

Auto installation
Manual installation

Create a project

The fastest way to start is with bun create elysia, which scaffolds a project with sensible defaults:

Scaffold the project

bun create elysia app

This creates an app folder with Elysia installed and a starter src/index.ts.

Enter the project directory

cd app

Start the development server

bun dev

Navigate to http://localhost:3000. You should see Hello Elysia.

The dev command uses Bun’s --watch flag to reload the server automatically on file changes.

Manual setup

If you prefer to set up a project from scratch, install Elysia and Bun type definitions:

Install dependencies

bun add elysia
bun add -d @types/bun

Create the entry point

Create src/index.ts with the following content:

import { Elysia } from 'elysia'

const app = new Elysia()
  .get('/', () => 'Hello Elysia')
  .listen(3000)

console.log(
  `Elysia is running at ${app.server?.hostname}:${app.server?.port}`
)

Add scripts to package.json

{
  "scripts": {
    "dev": "bun --watch src/index.ts",
    "build": "bun build src/index.ts --target bun --outdir ./dist",
    "start": "NODE_ENV=production bun dist/index.js",
    "test": "bun test"
  }
}

dev — runs with hot reload during development
build — compiles for production
start — runs the compiled output

Configure TypeScript

Create tsconfig.json or add the following to an existing one. Strict mode is required for Elysia’s type inference to work correctly:

{
  "compilerOptions": {
    "strict": true
  }
}

Install Node.js

brew install node

We recommend using TypeScript. Select the tab that matches your preference:

TypeScript
JavaScript

Install dependencies

Elysia on Node.js requires the @elysia/node adapter. Install Elysia, the adapter, and TypeScript tooling:

bun add elysia @elysia/node && \
bun add -d tsx @types/node typescript

tsx is a TypeScript runner with hot reload and modern dev tooling built in.

Create the entry point

Create src/index.ts:

import { Elysia } from 'elysia'
import { node } from '@elysia/node'

const app = new Elysia({ adapter: node() })
  .get('/', () => 'Hello Elysia')
  .listen(3000, ({ hostname, port }) => {
    console.log(`Elysia is running at ${hostname}:${port}`)
  })

Add scripts to package.json

{
  "scripts": {
    "dev": "tsx watch src/index.ts",
    "build": "tsc src/index.ts --outDir dist",
    "start": "NODE_ENV=production node dist/index.js"
  }
}

Initialize TypeScript

npx tsc --init

Then update tsconfig.json to enable strict mode:

{
  "compilerOptions": {
    "strict": true
  }
}

Using Elysia without TypeScript means you will miss out on automatic type inference, autocomplete, end-to-end type safety with Eden, and advanced compile-time checks — all of which are core features of the framework.

Install dependencies

bun add elysia @elysia/node

Create the entry point

Create src/index.js:

import { Elysia } from 'elysia'
import { node } from '@elysia/node'

const app = new Elysia({ adapter: node() })
  .get('/', () => 'Hello Elysia')
  .listen(3000, ({ hostname, port }) => {
    console.log(`Elysia is running at ${hostname}:${port}`)
  })

Add scripts to package.json

{
  "type": "module",
  "scripts": {
    "dev": "node src/index.js",
    "start": "NODE_ENV=production node src/index.js"
  }
}

WinterTC / Web Standard runtimes

Elysia is WinterTC compliant, meaning it runs on any framework or runtime that supports the Web Standard Request / Response API.

Install Elysia

bun install elysia

Choose a runtime

Select a platform that supports Web Standard Request/Response:

Cloudflare Workers

Deploy Elysia as a Cloudflare Worker.

Next.js

Use Elysia inside Next.js API routes.

Expo

Elysia as Expo App Router API routes.

Astro

Elysia as Astro API routes.

SvelteKit

Elysia as SvelteKit API routes.

Vercel

Elysia as Vercel Edge Functions.

Custom runtime fallback

If your runtime is not listed, expose app.fetch as the request handler:

import { Elysia } from 'elysia'

const app = new Elysia()
  .get('/', () => 'Hello Elysia')

export default app.fetch

Any runtime that accepts a (request: Request) => Response | Promise<Response> function is compatible.

Next steps

Now that your server is running, explore the core concepts:

Routing

Define routes, path parameters, query strings, and method handlers.

Validation

Validate requests at runtime using Elysia.t, Zod, Valibot, and more.

Eden client

Connect a frontend with end-to-end type safety and no code generation.

Plugins

Add CORS, JWT, OpenAPI, static files, and more with official plugins.

Get Started

Essential Concepts

Patterns

Eden (Type-safe Client)

Quick Start: run Elysia on Bun or Node.js

Install Bun

Create a project

Manual setup

Install Node.js

WinterTC / Web Standard runtimes

Cloudflare Workers

Next.js

Expo

Astro

SvelteKit

Vercel

Next steps

Routing

Validation

Eden client

Plugins

Build docs developers (and LLMs) love

Get Started

Essential Concepts

Patterns

Eden (Type-safe Client)

Documentation Index

​Install Bun

​Create a project

​Manual setup

​Install Node.js

​WinterTC / Web Standard runtimes

Cloudflare Workers

Next.js

Expo

Astro

SvelteKit

Vercel

​Next steps

Routing

Validation

Eden client

Plugins

Build docs developers (and LLMs) love

Install Bun

Create a project

Manual setup

Install Node.js

WinterTC / Web Standard runtimes

Next steps