Fastify vs Koa
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 fast, low-overhead web framework for building servers and APIs with Node.js.
Open source · MIT
Small Node.js web framework built on async functions for writing HTTP middleware.
The short answer
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
Choose Koa if you need…
- Node.js developers who want a minimal web framework they can shape themselves
- Teams building APIs or web servers who prefer async/await middleware
- Developers familiar with Express-style middleware who want a smaller core
Side-by-side
| Fastify | Koa | |
|---|---|---|
| Type | Library | Library |
| Price | Free and open source | Free and open source |
| Licence | MIT | MIT |
| GitHub stars | 37.3k | 35.7k |
| Setup difficulty | Beginner | Intermediate |
| How you get it | Install with a package manager | Install with a package manager |
| Main language | JavaScript | JavaScript |
| Last code update | 4 days ago | 4 days ago |
What each one is
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.
Koa
Koa is a web framework for Node.js that lets developers build HTTP servers and APIs by chaining middleware functions. It uses modern async/await syntax, so each step can pause, wait for work like a database call, and then pass control onward. Developers use it as a lightweight base they can extend with their own choice of add-ons.
Best for
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
Koa
- Node.js developers who want a minimal web framework they can shape themselves
- Teams building APIs or web servers who prefer async/await middleware
- Developers familiar with Express-style middleware who want a smaller core
Strengths
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
Koa
- Uses ES2017 async functions, so control flow reads top to bottom without callback nesting
- Minimal core keeps the framework small and lets you choose extra pieces
- MIT licensed and widely used, with a large star count on GitHub
Not ideal for
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
Koa
- Complete beginners new to Node.js, since Koa ships with little built in and assumes familiarity with HTTP and middleware
- Projects that need a full batteries-included framework out of the box, because routing, body parsing and similar features come from separate packages
Trade-offs
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
Koa
- Little is included by default, so routing and parsing require additional packages
- Public README was truncated here, so detailed API and version-specific behavior could not be verified from this entry
Getting started
Fastify
Install Fastify in an existing project
npm i fastifyGenerate a new Fastify project
npm init fastifyFrequently asked questions
What is the difference between Fastify and Koa?
Fastify: A fast, low-overhead web framework for building servers and APIs with Node.js. Koa: Small Node.js web framework built on async functions for writing HTTP middleware. Fastify suits node.js developers building json apis or backend services, while Koa suits node.js developers who want a minimal web framework they can shape themselves.
Are Fastify and Koa free?
Fastify: Free and open source. Koa: Free and open source.
Which is easier to set up, Fastify or Koa?
Fastify is easier to get started with (rated beginner); Koa is rated intermediate and usually needs more setup.
Is Fastify or Koa more popular?
Fastify has more GitHub stars (37.3k) than Koa (35.7k). Popularity isn't the same as fit — check which one matches your use case above.
What are other alternatives to Fastify and Koa?
Other options people compare them with include Express, Hono, Apollo Server.
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.