Quick Start

Elysia is a TypeScript backend framework with multiple runtime support but optimized for Bun.

However, you can use Elysia with other runtimes like Node.js.

<Tab id="quickstart" :names="['Bun', 'Node.js', 'Web Standard']" :tabs="['bun', 'node', 'web-standard']"

Elysia is optimized for Bun which is a JavaScript runtime that aims to be a drop-in replacement for Node.js.

You can install Bun with the command below:

::: code-group

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

powershell -c "irm bun.sh/install.ps1 | iex"

:::

<Tab id="quickstart" :names="['Auto Installation', 'Manual Installation']" :tabs="['auto', 'manual']"

We recommend starting a new Elysia server using bun create elysia, which sets up everything automatically.

bun create elysia app

Once done, you should see the folder name app in your directory.

cd app

Start a development server by:

bun dev

Navigate to localhost:3000 should greet you with "Hello Elysia".

::: tip Elysia ships you with dev command to automatically reload your server on file change. :::

To manually create a new Elysia app, install Elysia as a package:

bun add elysia
bun add -d @types/bun

This will install Elysia and Bun type definitions.

Create a new file src/index.ts and add the following code:

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}`
)

Open your package.json file and add the following scripts:

{
   	"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"
   	}
}

These scripts refer to the different stages of developing an application:

• dev - Start Elysia in development mode with auto-reload on code change.
• build - Build the application for production usage.
• start - Start an Elysia production server.

If you are using TypeScript, make sure to create, and update tsconfig.json to include compilerOptions.strict to true:

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

Node.js is a JavaScript runtime for server-side applications, the most popular runtime for JavaScript which Elysia supports.

You can install Node.js with the command below:

::: code-group

brew install node

choco install nodejs

sudo apt install nodejs

pacman -S nodejs npm

:::

Setup

We recommend using TypeScript for your Node.js project.

<Tab id="language" :names="['TypeScript', 'JavaScript']" :tabs="['ts', 'js']"

To create a new Elysia app with TypeScript, we recommend installing Elysia with tsx:

::: code-group

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

pnpm add elysia @elysiajs/node && \
pnpm add -D tsx @types/node typescript

npm install elysia @elysiajs/node && \
npm install --save-dev tsx @types/node typescript

yarn add elysia @elysiajs/node && \
yarn add -D tsx @types/node typescript

:::

This will install Elysia, TypeScript, and tsx.

tsx is a CLI that transpiles TypeScript to JavaScript with hot-reload and several more feature you expected from a modern development environment.

Create a new file src/index.ts and add the following code:

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

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

Open your package.json file and add the following scripts:

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

These scripts refer to the different stages of developing an application:

• dev - Start Elysia in development mode with auto-reload on code change.
• build - Build the application for production usage.
• start - Start an Elysia production server.

Make sure to create tsconfig.json

npx tsc --init

Don't forget to update tsconfig.json to include compilerOptions.strict to true:

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

::: warning If you use Elysia without TypeScript you may miss out on some features like auto-completion, advanced type checking and end-to-end type safety, which are the core features of Elysia. :::

To create a new Elysia app with JavaScript, starts by installing Elysia:

::: code-group

bun add elysia @elysiajs/node

pnpm add elysia @elysiajs/node

npm install elysia @elysiajs/node

yarn add elysia @elysiajs/node

:::

This will install Elysia, TypeScript, and tsx.

tsx is a CLI that transpiles TypeScript to JavaScript with hot-reload and several more feature you expected from a modern development environment.

Create a new file src/index.ts and add the following code:

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

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

Open your package.json file and add the following scripts:

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

These scripts refer to the different stages of developing an application:

• dev - Start Elysia in development mode with auto-reload on code change.
• start - Start an Elysia production server.

Make sure to create tsconfig.json

npx tsc --init

Don't forget to update tsconfig.json to include compilerOptions.strict to true:

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

Elysia is a WinterCG compliance library, which means if a framework or runtime supports Web Standard Request/Response, it can run Elysia.

First, install Elysia with the command below:

::: code-group

bun install elysia

pnpm install elysia

npm install elysia

yarn add elysia

:::

Next, select a runtime that supports Web Standard Request/Response.

We have a few recommendations:

Not on the list?

If you are using a custom runtime, you may access app.fetch to handle the request and response manually.

import { Elysia } from 'elysia'

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

export default app.fetch

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