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elysiajs/elysia

📈 Trending★ 18,357TypeScriptAudience · developerComplexity · 3/5ActiveLicenseSetup · easy

TLDR

TypeScript web server framework with end-to-end type safety, built for Bun runtime. Catches data type mismatches before your app runs.

Mindmap

mindmap
  root((Elysia))
    What it does
      HTTP server framework
      Type-safe endpoints
      Error prevention
    Tech Stack
      TypeScript
      Bun runtime
    Use Cases
      REST APIs
      Web services
      Type-safe backends
    Developer Experience
      Straightforward syntax
      Built-in validation
      Fast feedback

Things people build with this

USE CASE 1

Build REST APIs with automatic type checking between client and server code.

USE CASE 2

Create web services where data type errors are caught before deployment.

USE CASE 3

Develop HTTP endpoints with built-in validation and type safety.

Tech stack

TypeScriptBun

Getting it running

Difficulty · easy Time to first run · 5min

Requires Bun runtime to be installed; standard npm/bun install otherwise.

Use freely for any purpose including commercial, as long as you keep the copyright notice.

In plain English

Elysia is a web server framework written in TypeScript, designed to make building HTTP servers feel straightforward and developer-friendly. Its main selling points are end-to-end type safety, meaning errors caused by mismatched data types between different parts of your code can be caught before the app runs, and a focus on good developer experience. It is built to run on Bun, a JavaScript runtime environment. The readme is sparse and points to external documentation for details.

Copy-paste prompts

Prompt 1
Show me how to set up a basic Elysia server with type-safe route handlers.
Prompt 2
How do I define request and response types in Elysia to catch mismatches early?
Prompt 3
Create an example Elysia endpoint that validates incoming JSON and returns typed data.
Prompt 4
What's the difference between Elysia and Express, and when should I use Elysia?
Open on GitHub → Explain another repo

Generated 2026-05-18 · Model: sonnet-4-6 · Verify against the repo before relying on details.