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    React server-side rendering support for Fastify with Next.js framework.


    npm i fastify-nextjs next react react-dom --save


    Since Next.js needs some time to be ready on the first launch, you must declare your routes inside the after callback, after you registered the plugin. The plugin will expose the next API in Fastify that will handle the rendering for you.

    const fastify = require('fastify')()
      .after(() => {'/hello')
    fastify.listen(3000, err => {
      if (err) throw err
      console.log('Server listening on http://localhost:3000')

    All your server rendered pages must be saved in the folder pages, as you can see in the Next.js documentation.

    // /pages/hello.js
    export default () => <div>hello world</div>

    If you need to pass custom options to next just pass them to register as second parameter.

    fastify.register(require('fastify-nextjs'), { dev: true })

    If you need to handle the render part yourself, just pass a callback to next:'/hello', (app, req, reply) => {
      // your code
      // `app` is the Next instance
      app.render(req.raw, reply.raw, '/hello', req.query, {})

    If you need to render with Next.js from within a custom handler, use reply.nextRender

    app.setErrorHandler((err, req, reply) => {
      return reply.nextRender('/a')

    If you need to render a Next.js error page, use reply.nextRenderError

    app.setErrorHandler((err, req, reply) => {
      return reply.status(err.statusCode || 500).nextRenderError(err)

    If you need to handle POST routes, you can define the HTTP method:'/api/*', { method: 'GET' });'/api/*', { method: 'POST' });

    Assets serving

    By default plugin handle route ${basePath}/_next/* and forward to Next.js.

    If you have custom preprocessing for _next/* requests, you can prevent this this handling with noServeAssets: true property for plugin options:

      .register(require('fastify-nextjs'), {
        noServeAssets: true
      .after(() => {`${process.env.BASE_PATH || ''}/_next/*`, (app, req, reply) => {
          // your code
          app.getRequestHandler()(req.raw, reply.raw).then(() => {
            reply.sent = true


    The plugin includes under-pressure, which can be configured by providing an underPressure property to the plugin options.

    Using under-pressure allows implementing a circuit breaker that returns an error when the health metrics are not respected. Because React server side rendering is a blocking operation for the Node.js server, returning an error to the client allows signalling that the server is under too much load.

    The available options are the same as those accepted by under-pressure.

    For example:

    fastify.register(require('fastify-nextjs'), {
      underPressure: {
        exposeStatusRoute: true
    • underPressure - bool|object

      • (default) when false, under-pressure is not registered
      • when true, under-pressure is registered with default options
      • when it is an object, under-pressure is registered with the provided options

    Custom properties on the request object

    If you want to share custom objects (for example other fastify plugin instances - e.g. fastify-redis) across the server/client with each page request, you can use the onRequest hook to add it to the request object. Here is an example on how to do it:

    const Fastify = require('fastify')
    const FastifyRedis = require('fastify-redis')
    const FastifyNextJS = require('fastify-nextjs')
    const fastify = Fastify()
    fastify.register(FastifyRedis, { host: '' })
    fastify.register(function(instance) {
      // for performance reasons we do not want it to run on every request
      // only the nextjs one should run
      instance.addHook('onRequest', function(request, reply, done) {
        // define a custom property on the request
        request.raw.customProperty = { hello: "world" }
        // OR make the instance of fastify-redis available in the request
        request.raw.redisInstance = instance.redis
 '/', function(app, request, reply) {
        // your custom property containing the object will be available here
        // request.raw.customProperty
        // OR the redis instance
        // request.raw.redisInstance
        app.render(request.raw, reply.raw, '/hello', request.query, {})
    }, { prefix: '/hello' })

    In the example above we made the customProperty and redisInstance accessible in every request that is made to the server. On the client side it can be accessed like in this example:

    const CustomPropPage = ({ cp, ri }) => <div>custom property value: {cp} | redis instance: {ri}</div>;
    export default CustomPropPage;
    export const getServerSideProps = async function (ctx) {
      return {
        props: {
          cp: ctx.req.customProperty,
          ri: ctx.req.redisInstance,


    CI currently runs npm@6 so when upgrading packages, please use this version.


    This project is kindly sponsored by:


    Licensed under MIT.


    npm i fastify-nextjs

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    • matteo.collina
    • cemremengu