Elysia vs Fastify
Which should you use? A side-by-side look at what each one does, who it suits, what it costs, how hard it is to set up, and where each falls short.
Open source · MIT
A TypeScript web framework for building HTTP servers, designed to run on Bun.
Open source · MIT
A fast, low-overhead web framework for building servers and APIs with Node.js.
The short answer
Choose Elysia if you need…
- TypeScript developers building HTTP APIs or web servers
- Teams already using or willing to adopt the Bun runtime
- Projects that want type safety shared between server and client code
Choose Fastify if you need…
- Node.js developers building JSON APIs or backend services
- Teams that care about request throughput and want a lightweight framework
- Projects that want schema-based validation of routes and responses
- Developers who want to organize code into reusable plugins
Side-by-side
| Elysia | Fastify | |
|---|---|---|
| Type | Framework | Library |
| Price | Free and open source | Free and open source |
| Licence | MIT | MIT |
| GitHub stars | 19.3k | 37.3k |
| Setup difficulty | Intermediate | Beginner |
| How you get it | Install with a package manager | Install with a package manager |
| Main language | TypeScript | JavaScript |
| Last code update | 8 days ago | 4 days ago |
What each one is
Elysia
Elysia is a TypeScript framework for building web servers and HTTP APIs. Its README emphasizes end-to-end type safety and a developer-friendly experience, and says it is built to run on the Bun JavaScript runtime. Developers use it to define routes and handlers in TypeScript with types shared across the code.
Fastify
Fastify is a framework for building web servers and APIs in Node.js. You define routes, such as a URL that returns data, and Fastify handles incoming requests with minimal extra work per request. It also offers a plugin system, input and output validation using JSON Schema, and built-in logging through Pino.
Best for
Elysia
- TypeScript developers building HTTP APIs or web servers
- Teams already using or willing to adopt the Bun runtime
- Projects that want type safety shared between server and client code
Fastify
- Node.js developers building JSON APIs or backend services
- Teams that care about request throughput and want a lightweight framework
- Projects that want schema-based validation of routes and responses
- Developers who want to organize code into reusable plugins
Strengths
Elysia
- Written in TypeScript with a focus on end-to-end type safety
- Documentation is hosted separately at elysiajs.com with links from the README
- Active project with a recent push and an MIT license
Fastify
- The README reports high request throughput in a synthetic hello-world benchmark, with the caveat that real results depend on the application
- Supports JSON Schema validation and serialization for routes
- Includes a plugin architecture and hooks for extending behavior
Not ideal for
Elysia
- Developers who need to run on Node.js only, since the README ties the framework to Bun and this is not verified here
- Beginners new to both TypeScript and backend development, who may find the setup and concepts a lot to learn at once
- Projects that need a long track record of stability, given the pre-2.0 version number in the latest release
Fastify
- Beginners who have not yet learned Node.js basics, since the framework assumes JavaScript familiarity
- Projects that need a non-Node.js language, because Fastify is for Node.js only
- Teams expecting a large built-in feature set; much functionality comes from plugins, per the docs
Trade-offs
Elysia
- The README is short and defers most detail to external documentation
- Positioned around the Bun runtime, which limits the setup choices
- Some README claims, such as performance comparisons, are only summarized in a hidden image and are not verified here
Fastify
- Benchmark figures come from the maintainers' own synthetic test and may not match your workload
- The README's benchmark table lists an older Fastify version (4.0.0), so the numbers are not current
- Binding to 0.0.0.0 in containers requires care, since the README warns of security risks
Getting started
Elysia
Create a new app with the Elysia template
bun create elysia appFastify
Install Fastify in an existing project
npm i fastifyGenerate a new Fastify project
npm init fastifyFrequently asked questions
What is the difference between Elysia and Fastify?
Elysia: A TypeScript web framework for building HTTP servers, designed to run on Bun. Fastify: A fast, low-overhead web framework for building servers and APIs with Node.js. Elysia suits typescript developers building http apis or web servers, while Fastify suits node.js developers building json apis or backend services.
Are Elysia and Fastify free?
Elysia: Free and open source. Fastify: Free and open source.
Which is easier to set up, Elysia or Fastify?
Fastify is easier to get started with (rated beginner); Elysia is rated intermediate and usually needs more setup.
Is Elysia or Fastify more popular?
Fastify has more GitHub stars (37.3k) than Elysia (19.3k). Popularity isn't the same as fit — check which one matches your use case above.
What are other alternatives to Elysia and Fastify?
Other options people compare them with include Hono, Express, tRPC, Koa.
Keep comparing
Built from our catalogue entries for both products: open-source details come from each project's README (AI-assisted, refreshed weekly) and GitHub data; AI-tool details are editorial. Spotted something wrong? Let us know from either product's page.