Hono OpenAPI

hono-openapi is a middleware which enables automatic OpenAPI documentation generation for your Hono API by integrating with validation libraries like Zod, Valibot, ArkType, and TypeBox and all libs supporting Standard Schema.

🛠️ Installation

Install the package along with your preferred validation library and its dependencies:

npm install hono-openapi @hono/standard-validator

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🚀 Getting Started

1. Define Your Schemas

Define your request and response schemas using your preferred validation library. Here's an example using Valibot:

import * as v from 'valibot'

const querySchema = v.object({
  name: v.optional(v.string()),
})

const responseSchema = v.string()

---

2. Create Routes

Use describeRoute for route documentation and validation:

import { Hono } from 'hono'
import { describeRoute, resolver, validator } from 'hono-openapi'

const app = new Hono()

app.get(
  '/',
  describeRoute({
    description: 'Say hello to the user',
    responses: {
      200: {
        description: 'Successful response',
        content: {
          'text/plain': { schema: resolver(responseSchema) },
        },
      },
    },
  }),
  validator('query', querySchema),
  (c) => {
    const query = c.req.valid('query')
    return c.text(`Hello ${query?.name ?? 'Hono'}!`)
  }
)

Note:
When using validator() from hono-openapi, any validation added for query, json, param or form is automatically included in the OpenAPI request schema.
There’s no need to manually define request parameters inside describeRoute().

---

3. Generate OpenAPI Spec

Add an endpoint for your OpenAPI document:

import { openAPIRouteHandler } from 'hono-openapi'

app.get(
  '/openapi',
  openAPIRouteHandler(app, {
    documentation: {
      info: {
        title: 'Hono API',
        version: '1.0.0',
        description: 'Greeting API',
      },
      servers: [
        { url: 'http://localhost:3000', description: 'Local Server' },
      ],
    },
  })
)

---

Wanna explore more, check out our docs - https://honohub.dev/docs/openapi