OpenAPI 3 and 3.1 schema generator and validator for Hono, itty-router and more!
**Documentation**: chanfana.pages.dev
**Source Code**: github.com/cloudflare/chanfana
## Overview
[chanfana](https://github.com/cloudflare/chanfana) **(previously known as itty-router-openapi)** is a library that adds
OpenAPI schema generation and validation to any router (
Hono, itty-router, etc), meant to be a
powerful and lightweight
library for Cloudflare Workers but runs on any runtime supported by the base router.
The key features are:
- OpenAPI 3 and 3.1 schema generator and validator
- Zod v4 compatible with full TypeScript inference
- Fully written in typescript
- [Class-based endpoints](https://chanfana.pages.dev/endpoints/defining-endpoints)
- Query, Path, Headers, and Body typescript inference, see [Parameters](https://chanfana.pages.dev/endpoints/parameters) and [Request Validation](https://chanfana.pages.dev/endpoints/request-validation)
- Extend existing [Hono](https://chanfana.pages.dev/router-adapters), [itty-router](https://chanfana.pages.dev/router-adapters), etc application, without touching old routes
- CLI to extract the schema.json from your code (npx chanfana) - see [CLI Documentation](https://chanfana.pages.dev/cli)
## AI Skills
Chanfana provides AI coding assistant skills to help you build OpenAPI endpoints faster. Install them using [npx skills](https://www.npmjs.com/package/skills):
```bash
npx skills install cloudflare/chanfana
```
Available skills:
- **write-endpoints** - Comprehensive guide for building OpenAPI endpoints with schema definition, request validation, CRUD operations, and D1 integration
## Getting started
[](https://deploy.workers.cloudflare.com/?url=https://github.com/cloudflare/chanfana/tree/main/template)
Or scaffold it locally with the `create-cloudflare` CLI:
```bash
npm create cloudflare@latest -- --template https://github.com/cloudflare/chanfana/tree/main/template
```
The template includes a complete Task API with Hono, D1, and Zod v4 — full CRUD endpoints, a custom endpoint example, integration tests, and auto-generated docs at `/api/docs`.
See [`template/README.md`](template/README.md) for full setup instructions.
## Installation
```bash
npm i chanfana --save
```
## Command-Line Interface (CLI)
Chanfana includes a CLI tool to help you extract the OpenAPI schema from your Cloudflare Worker project. This is useful for generating a static schema file, for example, in CI/CD pipelines.
The basic command is:
```bash
npx chanfana
```
This will start your worker using `wrangler dev`, fetch the schema from `/openapi.json`, and save it to `schema.json`.
For more details on options and usage, please refer to the [**CLI Documentation**](https://chanfana.pages.dev/cli).
## Minimal Hono Example
```ts
import { fromHono, OpenAPIRoute } from 'chanfana'
import { Hono } from 'hono'
import { z } from 'zod'
export type Env = {
// Example bindings
DB: D1Database
BUCKET: R2Bucket
}
export type AppContext = Context<{ Bindings: Env }>
export class GetPageNumber extends OpenAPIRoute {
schema = {
request: {
params: z.object({
id: z.string().min(2).max(10),
}),
query: z.object({
page: z.number().int().min(0).max(20),
}),
},
}
async handle(c: AppContext) {
const data = await this.getValidatedData()
return c.json({
id: data.params.id,
page: data.query.page,
})
}
}
// Start a Hono app
const app = new Hono<{ Bindings: Env }>()
// Setup OpenAPI registry
const openapi = fromHono(app)
// Register OpenAPI endpoints (this will also register the routes in Hono)
openapi.get('/entry/:id', GetPageNumber)
// Export the Hono app
export default app
```
## Feedback and contributions
[chanfana](https://github.com/cloudflare/chanfana) aims to be at the core of new APIs built using
Workers and define a pattern to allow everyone to
have an OpenAPI-compliant schema without worrying about implementation details or reinventing the wheel.
chanfana is considered stable and production ready and is being used with
the [Radar 2.0 public API](https://developers.cloudflare.com/radar/) and many other Cloudflare products.
You can also talk to us in the [Cloudflare Community](https://community.cloudflare.com/) or
the [Radar Discord Channel](https://discord.com/channels/595317990191398933/1035553707116478495)
