---
title: "How to do Custom Domains with Fly"
description: "Custom Domains with Fly is an application guide for using Fly to proxy traffic or serve applications across multiple custom domains. It explains how to configure an NGINX server for external sites and how to attach host and domain names to Fly applications with the flyctl command line. For automated workflows, it describes the Fly GraphQL API operations for adding, removing, checking, and deleting hosts and associated certificates, and points to a repository of ready-rolled Node applications demonstrating the API. The guide's speed run retrieves an app's IPv4 and IPv6 addresses, adds corresponding A and AAAA DNS records, creates a certificate with flyctl, and uses another command to monitor issuance. The resulting setup provides auto-renewing Let's Encrypt TLS certificates, edge TLS, and HTTP/2 support; the guide also states that Fly applications have no limit on attached certificates and can scale on demand."
---

# How to do Custom Domains with Fly

[Fly.io](https://yomu.fyi/company/fly-io) · Mar 9, 2020

**Type:** Tutorial

## Summary

Custom Domains with Fly is an application guide for using Fly to proxy traffic or serve applications across multiple custom domains. It explains how to configure an NGINX server for external sites and how to attach host and domain names to Fly applications with the flyctl command line. For automated workflows, it describes the Fly GraphQL API operations for adding, removing, checking, and deleting hosts and associated certificates, and points to a repository of ready-rolled Node applications demonstrating the API. The guide's speed run retrieves an app's IPv4 and IPv6 addresses, adds corresponding A and AAAA DNS records, creates a certificate with flyctl, and uses another command to monitor issuance. The resulting setup provides auto-renewing Let's Encrypt TLS certificates, edge TLS, and HTTP/2 support; the guide also states that Fly applications have no limit on attached certificates and can scale on demand.

## Context

The guide addresses proxying traffic or serving applications for multiple custom domains, including branded applications that need unified proxying across domains.

## Approach / What changed

It uses NGINX for proxying, flyctl for attaching domains and managing certificates, and the Fly GraphQL API for automated host and certificate operations. The documented setup adds IPv4 and IPv6 DNS records, creates a certificate, and monitors its issuance.

## Takeaways

- A custom domain setup uses flyctl ips list to obtain IPv4 and IPv6 addresses, then requires corresponding A and AAAA records at the DNS provider.
- flyctl certs create and flyctl certs show are used to create a certificate for a domain and monitor certificate issuance.
- The guide states that Fly applications have no limit on attached certificates and support auto-renewing Let's Encrypt TLS certificates, edge TLS, and HTTP/2.

**Tags:** [DNS](https://yomu.fyi/topic/dns), [Fly](https://yomu.fyi/topic/fly), [nginx](https://yomu.fyi/topic/nginx), [TLS](https://yomu.fyi/topic/tls)

- Source: [Fly.io](https://fly.io/blog/how-to-custom-domains-with-fly)
- Source URL: https://fly.io/blog/how-to-custom-domains-with-fly
- Ingested by Yomu: 2026-09-02T12:00:22.271Z

[Read original post](https://fly.io/blog/how-to-custom-domains-with-fly)