What is Fly?

Fly is an Application Delivery Network (ADN) that accelerates dynamic application delivery. We use a global network of servers to accept visitor traffic, run middleware on requests, then route them to backend applications. With a few clicks, your visitors will access your sites faster and more securely.

Setting up a site

Create a site within the Fly web interface, then change your site's DNS at Fly. Visitors to your application will connect to the nearest Fly edge server, which handles HTTPS termination and intelligently routes requests to your backend applications.

As you connect more backends, you can adjust where and how you will route your visitors. For example, you can mount your application to then attach a GitHub Pages backend to, add a Ghost Blog to, or direct an API to You can send visitors from Germany to a German language backend or send visitors on a cellular connection a lightweight text-only page; seamless discovery and full control over your visitor's roundtrip.

Using Fly Middleware, you can run logic on visitors requests. You can enforce HTTPS, investigate and adapt to user location with Geo IP Lookup, use Render Speed Tracking to monitor application performance, apply intelligent Session Aware Routing for authentication and more.

As a cherry on top, the full end-to-end roundtrip between the visitor, our topographically distributed edge nodes, and the agent running next to your application is fully encrypted using HTTPS until SSL termination, then into a hardened SSH tunnel. Your data is secure until it arrives at your application.

Get Started

Where are your data centers?

We have data centers all over the world. The closer the edge node to the visitor, the faster your application will appear. Currently, we deliver applications from:

We use a network addressing and routing method called Anycast which is part of the Border Gateway Protocol, or BGP. BGP is the the core internet routing protocol. Using Anycast, we assign a single IP address across all the edge nodes, then send your visitors to the one which is topographically closest. Requests travel across fast backhaul connections to your applications.

An added bonus: our servers are secure physical servers with their own networking equipment. Fly does not use cloud-based servers for traffic delivery or routing.

How much does Fly cost?

Each month, your first 2,000,000 requests and 100GB of transfer are free.

After that, you'll be billed based on how many thousands of requests and GB of bandwidth that you consume:

Region Per 1000 Requests Bandwidth
North America $0.0035 $0.18
Europe $0.0045 $0.18
Asia Pacific $0.0045 $0.21
South America $0.0055 $0.25
Africa $0.0055 $0.25
Middleware and Rules

Each request includes the execution of 2 middleware and 2 rules. Extra middleware/rules work as a request multiplier. If a request runs 4 middleware it is billed as two requests. If a request runs 3 rules and no middleware, it's billed as two requests.

Quick start

1. Sign up

Create your account at

2. Add a Site

Let us know what domain you want your backends to link to. You can do this by clicking Add Site within the Dashboard. We ask that you provide us with a hostname and, optionally, a name to represent that hostname. You can add multiple hostnames to a site, for example and

3. Install the Fly Agent

Next, download the Fly Agent or use our public Docker repository to get the Docker image.

To guide you through the initial setup, we have our usage instructions. We also have tips on how to get started with the Fly agent if you are using Docker, Heroku or Kubernetes.

4. Deploy your app

Once you deploy your changes, your application will automatically connect to the Fly servers and start serving traffic. We'll generate a special preview link so you can verify everything works end-to-end before switching your domain over to us.

5. Update your DNS

The last step is to point your domain to the Fly servers. We have a handy guide to help you. We'll then be able to issue a valid SSL/TLS certificate for your domain using the Let's Encrypt API.

6. Fly

Congratulations! Your application is now connected to the Fly Global Load Balancer. You have end-to-end encryption, slick discovery, seamless routing, and access to our growing bounty of powerful middleware.


What is middleware?

Fly Middleware allows you to transmogrify visitor request and server response data. Depending on the Middleware, it could add data to the backend request headers, change body content, or send custom log or debug information at the end of each request. To your application, this looks like end-to-end HTTPS, Geo IP headers, Google Authentication, Session Aware Routing and more.

How much does Middleware cost?

Pricing for basic Middleware is clear and simple. Your first 50,000 requests are free. Pricing will vary depending on the Middleware.

What about Beta Middleware?

Powerful new Middleware will be showing up all the time. The newest will be marked with the Beta tag. These Middleware can be used free of charge until the tag is removed.

Built in Middleware

HTTPS Upgrader

We think that HTTPS is really important. Using the HTTPS Upgrader, you can redirect all your http requests to https. The Upgrader receives the highest priority and will always run first.

Geo IP Lookup

With Geo IP Lookup, you can detect your visitor's geographic location based on their IP address. Once active, we will add location headers to your requests. Your application can then use these headers to change behavior based on user geography. For example, you can serve a localized German version of your pages to those with a Fly-IP-Counter-Name of Germany.

The Geo IP headers are:

Connection Speed Lookup

Using Connection Speed Lookup, you can detect a visitor's connection speed. After you enable this middleware, we will add the Fly-Connection-Type header to all of your requests. You can then use this information to optimize performance based on connection speed. For example, if your users are on a cellular network, you can serve them a 'low bandwidth' version of your application.

Possible header values are:

Render Speed Tracking

Render Speed Tracking will give you a fresh and accurate look into site rendering speeds over time. The tracker injects a small piece of javascript into your HTML requests to log client side render speeds. Within the Fly control panel, the 50th, 75th and 90th percentile render speeds are graphed within the Performance tab.

Google Analytics

With Fly, you can inject Google Analytics directly into your requests. To add it, click configure and enter your Google Analytics ID. Don't have one? Get started with Google Analytics here.

The Google Analytics Middleware is in beta.

Google Authentication

The Google Auth Middleware allows you to define restrictive authentication rules within your site. We attach an encrypted Fly-Google-Auth-User-JWT header to your requests, allowing you to 'gate' application functions behind the Google OpenID Connect protocol. For more information on how to write Google Authentication into your application, check out our guide.

The Google Authentication Middleware is in beta.

Rails 4+ Session Aware Routing

Sessions, like cookies, are used to store information about the visiting client. Within Rails, a session is similar to a cookie but - in Rails 4 or greater - encrypts its contents. With Rails 4+ Session Aware Routing, we are able to decrypt, analyze, and action session related information.

This enables you to route requests to specific backends and react to the information stored within the sessions. For example, your users who have a session indicating 'logged in' will receive your application while new or returning users will visit your marketing page to register or login.

The Rails 4+ Session Aware Routing Middleware is in beta.

Can I write my own?

Almost! If you are interested in writing your own middleware, please email Developers will soon be able to augment their application functionality with custom logic that runs close to users. Middleware can either be specific to a single app, or made available to all customers.

The Fly Agent

What is the Fly agent?

The Fly Agent is a binary that sits beside your application. Its job is to provide seamless service discovery, encrypt traffic between the Load Balancer and your application, and help weave in Middleware.

In most Load Balancing scenarios, an HTTPS connection becomes exposed after SSL Termination. Your data may move unencrypted as it travels within your data center - or even more perilous - to your co-located CDNs or application servers. The Fly Agent fixes this problem by routing your traffic through an SSH tunnel that encrypts your data after SSL-Termination until it arrives at your application.

With topographically distributed edge nodes we shorten SSL Termination to improve performance then blast the traffic through secure SSH tunnels. You receive true end-to-end encryption. There is no need for you to setup any SSL/TLS certificates; Fly issues SSL/TLS certificates for you automatically using the Let's Encrypt API. You verify your hostname, add the agent to your backends, then get right to the magic of simplified application delivery: slick service discovery, easy routing and powerful Middleware.

For a deeper primer on the state of HTTPS, how it works, its impact on network and server performance, and how Fly changes things, check out this document.

How does it work?

The Fly Agent spawns small programs that run alongside your web application servers. Using strong ciphers, we create an encrypted connection that is used as a tunnel for transporting data to and from your servers. Our tunnels are connected through SSH remote port forwarding. Each instance of the Fly Agent uses SSH to both authenticate and encrypt the data.

Doesn't it cause TCP-over-TCP performance issues?

Nope! SSH tunneling doesn't encapsulate full TCP packets. It extracts data from each packet and sends it over an encrypted session. Our tunnels have a negligible impact on per request latency, comparable to the latency cost of doing end-to-end SSL/TLS in a traditional load balancing configuration.

Learn More Download


Mounting a GitHub Pages Backend

Fly allows you to use GitHub Pages as an SSL/TLS secure back-end associated with your hostname. A excellent example case for this is attaching a GitHub Pages repository to your domain at /docs/ to host your documentation. For example, our documentation is hosted on GitHub pages and is being served through Fly via HTTPS to this URL - neat, eh?

First, you will need to have a verified hostname. If you see green checkmarks under Verified and DNS Configured, then we are good to go.

Access the hostname you would like to attach GitHub Pages to then visit the Routing page. Within the Routing page, click Add Backend. You will then have three fields to enter:

Once the backend has been created, it will have a routing rule specifying the path you have selected.

You will now be able to access your GitHub pages from that path!

This is a quick, no-cost way of hosting your own documentation, easily securing it via SSL/TLS and attaching it to your own domain name. You should be aware of the usage limits before rolling this out to thousands of users.

Mounting a Heroku Backend

Once you have verified your hostname, the next step is to add a backend. If you host your application on Heroku, you can take advantage of the Heroku Backend.

Access the hostname that you would like to associate with your Heroku application. Click within the Routing tab, then under Backends select Add a Backend.

You will now be able to select Heroku. Provide a name for the application, like Application, Store, or whatever feels good for you. Next, you need to provide the Heroku repository name - then, create it. For example, if you access your Heroku application by visiting:, you would enter infinite-beach-71880.

The next step is to attach the Fly agent to your application. We can do this by adding the Fly buildpack; after adding the backend, you receive a backend token and a Heroku command to add the buildpack.

heroku buildpacks:add
heroku config:set FLY_TOKEN=2c2d3b67b92bee86d919ffbf8f429eac83d86fc06721cde9421de73db5cd666a

Within your Heroku initialized repository, enter the commands above. Finally, push to the changes up to master.

git push heroku master

Fly will detect the agent immediately. The final step is to click Add a routing rule; here, you can specify how this application will be accessed relative to your hostname. If you would like to set your new Heroku application on the root of the domain, /, simply add / as the Path to match.

Once the rule has been added, you are done! Your Heroku application is now attached to the Fly Global Load Balancer.


We are here to help! We offer email based support. You can email us at

If you need SLAs, guaranteed response times, or things of that nature, please contact us.