ElysiaJS

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Ergonomic Framework for Humans

TypeScript with End-to-End Type Safety, type integrity, and exceptional developer experience. Supercharged by Bun.

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bun create elysia app

See why developers love Elysia

The first production ready,
and most loved Bun framework

Our Principle

Design for Human

Our goal is to design an ergonomic, sensible, and productive framework that even beginners can use easily

Designed to avoid unnecessary complexity and type complexity for you to focus on building

A framework that feels just like JavaScript

typescript
import { Elysia } from 'elysia'

new Elysia()
	.get('/', 'Hello World')
	.get('/image', Bun.file('mika.webp'))
	.get('/stream', function* () {
		yield 'Hello'
		yield 'World'
	})
	.ws('/realtime', {
		message(ws, message) {
			ws.send('got:' + message)
		}
	})
	.listen(3000)

Just Return

A string, number or complex JSON

All we need to do is just return

File built-in

To send a file or image, just return

Nothing more or nothing less

Stream response

Use yield to stream response

All we need to do is just return

Data in realtime

With µWebSocket built-in

Send live data in just 3 lines

The Next Level of Type Safety

typescript
import { 
Elysia
 } from 'elysia'

new 
Elysia
()
	.
get
('/id/:id', ({ 
params
, 
set
 }) => {




		
set
.
headers
.a



		return 'Su'
	})

	.
get
('/optional/:name?', ({ 
params
: { 
name
 } }) => {
        return 
name
 ?? 'Pardofelis'
	})
	.
listen
(3000)

Your own documentation in 1 line

It's not magic

With deep integration with OpenAPI schema
Elysia can generate Swagger documentation for your API out of the box

Scalar documentation generated by Elysia using Elysia Swagger plugin
typescript
import { Elysia } from 'elysia'
import swagger from '@elysiajs/swagger'

new Elysia()
	.use(swagger())
	.use(character)
	.use(auth)
	.listen(3000)

11.88ms

POST /character/:id/chat

Playback

Request
Validation
Transaction
Upload
Sync
For DevOps

OpenTelemetry

Elysia has 1st party support for OpenTelemetry. Instrumentation is built-in, so you can easily monitor your services on regardless of the platform.

typescript
import { 
treaty
 } from '@elysiajs/eden'
import type { 
App
 } from './server'

const 
api
 = 
treaty
<
App
>('api.elysiajs.com')

const { 
data
 } = await 
api
.
profile
.
patch
({
    
age
: 21
})
For Frontend

End-to-end Type Safety

Like tRPC, Elysia provides type-safety from the backend to the frontend without code generation. Interaction between frontend and backend is type-checked at compile time.

21x

faster than Express

6x

faster than Fastify

  1. Elysia Bun
    2,454,631 reqs/s
  2. Gin Go

    676,019

  3. Spring Java

    506,087

  4. Fastify Node

    415,600

  5. Express Node

    113,117

  6. Nest Node

    105,064

Measure in requests/second. Result from TechEmpower Benchmark Round 22 (2023-10-17) in PlainText

Test with confidence

Type safe with auto-completion

Elysia provide a type-safe layer for interact and test your server from routes to parameters.

With auto-completion, you can easily write tests for server without any hassle.

typescript
import { 
treaty
 } from '@elysiajs/eden'
import { 
app
 } from './index'
import { 
test
, 
expect
 } from 'bun:test'

const 
server
 = 
treaty
(
app
)


test
('should handle duplicated user', async () => {
	const { 
error
 } = await 
server
.
user
.
put
({
Argument of type '{ username: string; }' is not assignable to parameter of type '{ username: string; password: string; }'.
  Property 'password' is missing in type '{ username: string; }' but required in type '{ username: string; password: string; }'.
	    
username
: 'mika',
	})

	
expect
(
error
?.
value
).
toEqual
({
		
success
: false,
		
message
: 'Username already taken'
	})
})

Powered by love
from the community

Aqueel

@AqueelMiq

Jetfuel on bun at X! @shlomiatar who built the framework has an eye for picking the right tools for the job.

Shlomi Atar

@shlomiatar

also a shoutout to @saltyAom and the phenomenal Elysia js that is powering our server driven UI. Incredible work.

htmx.org

@htmx_org

htmx works great w/ @bunjavascript, @elysiaJS and @tursodatabase btw

Marc Laventure

@MarcLaventure

both engineering+monetary contributions are paramount for OSS we proudly sponsor dozens of projects: @elysiaJS @LitestarAPI @honojs @daveshanley @kevin_jahns @MarijnJH & help maintain repos+contribute to OSS at blistering cadence. it's @scalar's ethos to be a catalyst for OSS

Jarred Sumner

@jarredsumner

You can use Express with Bun, but often we see people using Elysia, Hono, or Bun.serve() directly.

Runyasak Ch. 💚

@runyasak

Started using @elysiaJS to create a Discord Bot and found the type system beautifully easy. DX is fantastic and coding is fun! Use @DrizzleORM with PostgreSQL. So much easier than I've used before. ElysiaJS has proved to me that great performance and DX can live together. 😎

Herrington Darkholme

@hd_nvim

Was introduced to @elysiaJS today and it looks pretty solid. end-to-end type safety/guard/swapper are killer features of the modern web! (and it's fast)

scalar.com

@scalar

so excited to be part of the amazing @elysiaJS community!

José Donato 🦋

@josedonato__

handling tables with ~350k rows like it's nothing. Working on allowing @ag_grid server side row model when connecting a custom backend to @openbb_finance Terminal Pro. Backend in @elysiaJS + @bunjsproject.

pilcrowonpaper

@pilcrow

Just in time for Bun 1.0 - Lucia 2.5 now supports @elysiajs out of the box!! You can also use Bun.serve() directly as well. This release also comes with 2 new OAuth providers, Strava and AWS Cognito!

MikroORM

@MikroORM

I've been playing a bit with @bunjavascript and @elysiaJS, need to do a few more tweaks before the release, but next version should work more natively with bun when it comes to TS support detection, e.g. the CLI works without ts-node installed.

Made possible by you

Elysia is not own by an organization but is driven by the community.
Elysia development is only possible thanks to your support

Become a sponsor

Thank you for making Elysia possible

To summarize
Only the best
for the bold

For builders, inventors, and visionaries
We spent years studying the strengths and weaknesses of JavaScript frameworks, all to deliver an exceptional experience

At the speed of light

Up to 21x faster than Express

Supercharged by Bun,

Elysia is one of top performing JavaScript frameworks

Maximum Type Safety

Dynamic type safety

Built from type to runtime

Elysia learn from your codebase, adapt, enforce with your type

Productive in a reach

The best experience of today

Ergonomically designed for human, putting DX at the priority. No technical non-sense

These are the pillars we built Elysia upon,
to deliver the best experience yet

Build the future,
together

Get startedTutorial

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