FusionAuth + Fastify: Using Links with Google & X.com (Twitter)

An example Fastify application showing how to use FusionAuth "links" to connect user accounts with external providers like Google and X.com (Twitter). The repository also includes a Docker‑based FusionAuth instance configured with Kickstart to speed up local development.

• Example application location: ./complete-application/
• FusionAuth via Docker Compose: ./docker-compose.yml + ./kickstart/ + ./.env

Follow the blog post Multi-Platform Video Uploads: Using Identity Provider Links for a detailed explanation of how to set up and use this example.

And check out the official documentation for more information on FusionAuth and Fastify:

• FusionAuth documentation: https://fusionauth.io/docs/
• Fastify documentation: https://fastify.dev/docs/

Prerequisites

• Docker and Docker Compose (for running FusionAuth locally)
• Node.js 22+ (Node 24+ recommended) and npm
• Internet access for installing dependencies and configuring external identity providers Google and X.com (Twitter)

Start FusionAuth with Docker

This repository includes a ready‑to‑run FusionAuth instance using Docker Compose. From the repository root:

docker compose up -d

• FusionAuth Admin UI will be available at: http://localhost:9011
• Kickstart files in ./kickstart/ will auto‑configure a tenant and application on first boot.

If you need to customize credentials or ports, create/update a .env file in the repo root to override variables used by docker-compose.yml.

The Identity Providers (IdPs) like Google and X.com (Twitter) are not preconfigured. You will need to set them up in the FusionAuth Admin UI after starting the service.

Run the Fastify example app

Install dependencies and start the app in development mode:

cd complete-application
npm install
npm run dev

By default the app will start on http://localhost:3000.