Follow the steps below to get started with Cosmic to power content for your Fastify application.

Create folder and install Fastify

mkdir cosmic-fastify
cd cosmic-fastify
npm init
npm i express

Install the Cosmic JavaScript SDK

Install the Cosmic JavaScript SDK in the location of the codebase.

npm i @cosmicjs/sdk

Add an Object type in the Cosmic dashboard

Log in to the Cosmic dashboard and create a new Blog Posts Object type in a new or existing Project with the following metafields:

  1. Image: Image type with key image
  2. Content: Rich text with key content

Blog model

Add content

Add a few blog posts to get some content ready to be delivered.

Create a new file app.js and add the following:

// app.js
import Fastify from 'fastify';
const fastify = Fastify({
  logger: true,
import { createBucketClient } from '@cosmicjs/sdk';
const cosmic = createBucketClient({
  bucketSlug: process.env.BUCKET_SLUG || '',
  readKey: process.env.BUCKET_READ_KEY || '',

fastify.get('/', async (request, reply) => {
  reply.header('Content-Type', 'text/html; charset=utf-8');

  const { objects: posts } = await cosmic.objects
      type: 'blog-posts',
  let html = '';
  posts?.map((post) => {
    html += `<div>
  return html;

const start = async () => {
  try {
    await fastify.listen({ port: 3000 });
  } catch (err) {

Add your Cosmic API keys

In a new file titled .env.local add the following environment variables and make sure to switch out the values with your Cosmic API keys found in Project / API keys.

# .env.local

Start the app

Start your app with the following command, go to http://localhost:3000, and see your blog posts. Note: we are using bun which enables environment variable reading without a separate package and the ability to use ES6 imports.

bun app.js