Elysia
UnclaimedAn ergonomic, high-performance TypeScript framework for building web servers and APIs.
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Tracked since2026
0 reviews trackedThe Bottom Line
Entry price
Free, no paid tier
Biggest pro
Exceptional performance, especially when paired with Bun
Biggest con
Performance benchmarks are heavily tied to Bun, which might not be the preferred runtime for all users
TL;DR - Elysia
- High-performance TypeScript framework for web servers.
- Automatic OpenAPI generation from TypeScript code.
- Optimized for Bun, but web-standard compatible for broader deployment.
Pricing: Free forever
Best for: Individuals & startups
What is Elysia?
Elysia is a fast and ergonomic TypeScript framework designed for building web servers and APIs. It leverages Bun's performance capabilities while maintaining web-standard compatibility, allowing it to run in various environments. The framework emphasizes a developer-friendly experience with strong type inference and automatic OpenAPI specification generation directly from TypeScript code.
It caters to developers looking for a high-performance solution for their backend services, especially those working with TypeScript and seeking an efficient development workflow. Elysia aims to combine speed with excellent developer experience, offering features like file handling, streaming, WebSockets, and robust validation with popular libraries such as Zod, Valibot, and ArkType.
The core benefit of Elysia is its ability to deliver exceptional performance, as demonstrated by benchmark results, without sacrificing the benefits of a well-typed and intuitive development environment. Its automatic OpenAPI generation significantly streamlines API documentation, making it easier to maintain and consume APIs.
Available on: Web
Pros & Cons
Pros
- Exceptional performance, especially when paired with Bun
- Excellent developer experience due to strong TypeScript integration and type inference
- Automated OpenAPI generation simplifies API documentation
- Flexible validation options with support for multiple schema libraries
- Web-standard approach allows for broader runtime compatibility
Cons
- Performance benchmarks are heavily tied to Bun, which might not be the preferred runtime for all users
- Newer framework, so community resources and plugins might be less mature than older alternatives
Preview
Key Features
High-performance web server capabilities (e.g., 2.4M reqs/s with Bun)Automatic OpenAPI specification generation from TypeScriptStrong type inference for improved developer experienceSupport for file handling and streamingWebSocket integrationBuilt-in validation with popular libraries (TypeBox, Zod, Valibot, ArkType, Effect)Macro system for reusable logic (e.g., authentication)Web-standard compatibility for flexible deployment (not vendor-locked to Bun)
Pricing
Free
Elysia is completely free to use with no hidden costs.
Reviews
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Elysia FAQ
How does Elysia achieve its high performance compared to other frameworks like Express or Fastify?
Elysia is optimized for Bun, leveraging its speed and efficiency. Benchmarks show Elysia on Bun achieving significantly higher requests per second (2,454,631 reqs/s) compared to Node.js frameworks like Fastify (415,600 reqs/s) or Express (113,117 reqs/s).
Can Elysia automatically generate OpenAPI specifications for my API?
Yes, Elysia can generate OpenAPI specifications directly from your TypeScript code. This process requires no annotations, configuration, or separate CLI commands, and it integrates with various TypeScript libraries like Prisma or Drizzle.
What validation libraries are supported by Elysia for defining request bodies?
Elysia supports a variety of validation libraries for defining request bodies, including its native TypeBox integration. It also provides examples for using Zod, Valibot, ArkType, and Effect for schema definition.
How does Elysia handle file uploads and streaming responses?
Elysia provides built-in capabilities for handling file uploads, such as accepting a file of a specific type like an image in a PUT request. It also supports streaming responses, allowing you to yield data incrementally.
Is Elysia tied exclusively to the Bun runtime, or can it be used with other JavaScript runtimes?
While Elysia is optimized for Bun and achieves its peak performance there, it is built on Web-Standards. This design choice allows Elysia to run on other JavaScript runtimes as well, preventing vendor lock-in.
Source: elysiajs.com