@fastify/swagger-ui

A Fastify plugin for serving Swagger UI.

Install

npm i @fastify/swagger-ui

Compatibility

Plugin version	Fastify version	Swagger Plugin Version
^5.x	^5.x	^9.x
^2.x	^4.x	^8.x
^1.x	^4.x	^8.x

Please note that if a Fastify version is out of support, then so are the corresponding version(s) of this plugin in the table above. See Fastify's LTS policy for more details.

Usage

Add it with @fastify/swagger to your project with register, pass it some options, call the swagger API, and you are done!

const fastify = require('fastify')()

await fastify.register(require('@fastify/swagger'))

await fastify.register(require('@fastify/swagger-ui'), {
  routePrefix: '/documentation',
  uiConfig: {
    docExpansion: 'full',
    deepLinking: false
  },
  uiHooks: {
    onRequest: function (request, reply, next) { next() },
    preHandler: function (request, reply, next) { next() }
  },
  staticCSP: true,
  transformStaticCSP: (header) => header,
  transformSpecification: (swaggerObject, request, reply) => { return swaggerObject },
  transformSpecificationClone: true
})

fastify.put('/some-route/:id', {
  schema: {
    description: 'post some data',
    tags: ['user', 'code'],
    summary: 'qwerty',
    params: {
      type: 'object',
      properties: {
        id: {
          type: 'string',
          description: 'user id'
        }
      }
    },
    body: {
      type: 'object',
      properties: {
        hello: { type: 'string' },
        obj: {
          type: 'object',
          properties: {
            some: { type: 'string' }
          }
        }
      }
    },
    response: {
      201: {
        description: 'Successful response',
        type: 'object',
        properties: {
          hello: { type: 'string' }
        }
      },
      default: {
        description: 'Default response',
        type: 'object',
        properties: {
          foo: { type: 'string' }
        }
      }
    },
    security: [
      {
        "apiKey": []
      }
    ]
  }
}, (req, reply) => {})

await fastify.ready()

API

Register options

Options

Option	Default	Description
baseDir	undefined	Specify the directory where all spec files that are included in the main one using $ref will be located. By default, this is the directory where the main spec file is located. Provided value should be an absolute path without trailing slash.
initOAuth	{}	Configuration options for Swagger UI initOAuth.
routePrefix	'/documentation'	Overwrite the default Swagger UI route prefix.
staticCSP	false	Enable CSP header for static resources.
transformStaticCSP	undefined	Synchronous function to transform CSP header for static resources if the header has been previously set.
transformSpecification	undefined	Synchronous function to transform the swagger document.
transformSpecificationClone	true	Provide a deepcloned swaggerObject to transformSpecification
uiConfig	{}	Configuration options for Swagger UI.
uiHooks	{}	Additional hooks for the documentation's routes. You can provide the onRequest and preHandler hooks with the same route's options interface.
theme	{}	Add custom JavaScript and CSS to the Swagger UI web page
logLevel	info	Allow to define route log level.

The plugin will expose the documentation with the following APIs:

URL	Description
'/documentation/json'	The JSON object representing the API
'/documentation/yaml'	The YAML object representing the API
'/documentation/'	The swagger UI
'/documentation/*'	External files that you may use in $ref

uiConfig

To configure Swagger UI, you need to modify the uiConfig option. It's important to ensure that functions are self-contained. Keep in mind that you cannot modify the backend code within the uiConfig functions, as these functions are processed only by the browser. You can reference the Swagger UI element using ui, which is assigned to window.ui.

Example

const fastify = require('fastify')()

await fastify.register(require('@fastify/swagger'))

await fastify.register(require('@fastify/swagger-ui'), {
  uiConfig: {
    onComplete: function () {
      alert('ui has type of ' + typeof ui) // 'ui has type of object'
      alert('fastify has type of ' + typeof fastify) // 'fastify has type of undefined'
      alert('window has type of ' + typeof window) // 'window has type of object'
      alert('global has type of ' + typeof global) // 'global has type of undefined'
    }
  }
})

transformSpecification

There can be use cases, where you want to modify the swagger definition on request. E.g. you want to modify the server definition based on the hostname of the request object. In such a case you can utilize the transformSpecification-option.

Example

const fastify = require('fastify')()

await fastify.register(require('@fastify/swagger'))

await fastify.register(require('@fastify/swagger-ui'), {
  transformSpecification: (swaggerObject, req, reply) => {
    swaggerObject.host = req.hostname
    return swaggerObject
  }
})

By default fastify.swagger() will be deepcloned and passed to the transformSpecification-function, as fastify.swagger() returns a mutatable Object. You can disable the deepcloning by setting transformSpecificationClone to false. This is useful, if you want to handle the deepcloning in the transformSpecification function.

Example with caching

const fastify = require('fastify')()
const LRU = require('tiny-lru').lru
const rfdc = require('rfdc')()

await fastify.register(require('@fastify/swagger'))

const swaggerLru = new LRU(1000)
await fastify.register(require('@fastify/swagger-ui'), {
  transformSpecificationClone: false,
  transformSpecification: (swaggerObject, req, reply) => {
    if (swaggerLru.has(req.hostname)) {
      return swaggerLru.get(req.hostname)
    }
    const clonedSwaggerObject = rfdc(swaggerObject)
    clonedSwaggerObject.host = req.hostname
    swaggerLru.set(req.hostname, clonedSwaggerObject)
    return clonedSwaggerObject
  }
})

theme

You can add custom JavaScript and CSS to the Swagger UI web page by using the theme option.

Example

const fastify = require('fastify')()

await fastify.register(require('@fastify/swagger'))

await fastify.register(require('@fastify/swagger-ui'), {
  theme: {
    title: 'My custom title',
    js: [
      { filename: 'special.js', content: 'alert("client javascript")' }
    ],
    css: [
      { filename: 'theme.css', content: '* { border: 1px red solid; }' }
    ],
    favicon: [
      {
        filename: 'favicon.png',
        rel: 'icon',
        sizes: '16x16',
        type: 'image/png',
        content: Buffer.from('iVBOR...', 'base64')
      }
    ]
  }
})

You can add custom JavaScript and CSS to the Swagger UI web page by using the theme option.

logo

It's possible to override the logo displayed in the top bar by specifying:

await fastify.register(require('@fastify/swagger-ui'), {
  logo: {
    type: 'image/png',
    content: Buffer.from('iVBOR...', 'base64'),
    href: '/documentation',
    target: '_blank'
  },
  theme: {
    favicon: [
      {
        filename: 'favicon.png',
        rel: 'icon',
        sizes: '16x16',
        type: 'image/png',
        content: Buffer.from('iVBOR...', 'base64')
      }
    ]
  }
})

Protect your documentation routes

You can protect your documentation by configuring an authentication hook. Here is an example using the @fastify/basic-auth plugin:

Example

const fastify = require('fastify')()
const crypto = require('node:crypto')

await fastify.register(require('@fastify/swagger'))

// perform constant-time comparison to prevent timing attacks
function compare (a, b) {
  a = Buffer.from(a)
  b = Buffer.from(b)
  if (a.length !== b.length) {
    // Delay return with cryptographically secure timing check.
    crypto.timingSafeEqual(a, a)
    return false
  }

  return crypto.timingSafeEqual(a, b)
}

await fastify.register(require('@fastify/basic-auth'), {
  validate (username, password, req, reply, done) {
    let result = true
    result = compare(username, validUsername) && result
    result = compare(password, validPassword) && result
    if (result) {
      done()
    } else {
      done(new Error('Access denied'))
    }
  },
  authenticate: true
})

await fastify.register(require('@fastify/swagger-ui', {
  uiHooks: {
    onRequest: fastify.basicAuth
  }
})

Rendering models at the bottom of the page

To ensure that models are correctly rendered at the bottom of the Swagger UI page, it's important to define your schemas using $refs through fastify.addSchema. Directly embedding JSON schemas within the schema property of your route definitions in Fastify may lead to them not being displayed in Swagger UI.

validatorUrl

SwaggerUI can automatically validate the given specification using an online validator. To enable this behavior you can pass the validatorUrl option to this plugin which will be forwarded to SwaggerUI.

await fastify.register('@fastify/swagger-ui', {
  validatorUrl: 'https://validator.swagger.io/validator'
})

Note that this behavior is disabled by default in @fastify/swagger-ui.

Bundling

To bundle Swagger UI with your application, the swagger-ui static files need to be copied to the server and the baseDir option set to point to the file directory.

Copy files with esbuild

import { build } from 'esbuild'
import { copy } from 'esbuild-plugin-copy'

await build({
  // ...
  plugins: [
    copy({
      resolveFrom: 'cwd',
      assets: {
        from: ['node_modules/@fastify/swagger-ui/static/*'],
        to: ['dist/static'],
      },
    }),
  ],
})

Copy files with docker

COPY ./node_modules/@fastify/swagger-ui/static /app/static

Configure Swagger UI to use a custom baseDir

Set the baseDir option to point to your folder.

await fastify.register(require('@fastify/swagger-ui'), {
  baseDir: isDev ? undefined : path.resolve('static'),
})

License

Licensed under MIT.