JavaScript at the Edge
Open source

Fly is a global JavaScript runtime that makes apps faster. You can optimize images, pre-render, cache partials, and more.

How does it work?

We run datacenters all over the world. When you deploy a Fly Edge Application, your visitors are routed to the nearest datacenter. Our application servers connect them to your JavaScript environment (built on v8) in under 1ms. Your app does the rest.

Illustrated balloon mascot scrapbooking — Optimize images
Deliver the exact images you need for each person. Use our Image and HTML APIs to enable responsive images without touching crufty old code no one remembers how to deploy.
`image.resize(800).webp()`
`const resp = await fetch("/articles/hero.jpg") const original = new fly.Image(resp.arrayBuffer()) let image = original.resize(800).withoutEnlargement() // webp for browsers that support it if (webpAllowed(req.headers.get("accept"))) { image = image.webp() resp.headers.set("content-type", "image/webp") } image = await image.toImage() return new Response(image.data, resp)`

Two illustrated balloon mascots playing Madlibs — Remix everything
Pull your content from anywhere, present it how you want and skip the copy pasta. We use this to inject our README.md into our documentation.
`html = markdown(await readme.text())`
const [layout, readme] = await Promise.all([ // fetch these in parallel! fetch("/docs/apps/"), fetch("/superfly/fly/master/README.md") ]) const doc = Document.parse(await layout.text()) // render readme const html = markdown(await readme.text()) const el = doc.querySelector("section.content") el.replaceWith(`<section>${html.body}</section>`) // send the new html return new Response(doc.outerHTML, layout)

Illustrated balloon mascot taking a selfie while it blows glass — Prerender for speed
The fastest way to serve a React app to a new visitor is to pre-render to HTML, then deliver the JavaScript later. Just write a few lines of edge JavaScript to load your existing React app and send it to your users.
`ReactDOMServer.renderToString(<MyApp />)`
`import React from 'react' import ReactDOMServer from 'react-dom/server' fly.http.respondWith(function preRender(resp) { const app = React.createElement( "MyButton", { color: 'blue', shadowSize: 2 }, 'Click Me' ) const html = ReactDOMServer.renderToString(app) return new Response(html) })`

Features

Our open source Edge Application runtime works like most modern application frameworks. We have tools for development + test, and powerful APIs for building CDN like applications.

Modern JavaScript spot graphic — Modern JavaScript
Write modern JavaScript with all the async/await goodness available in V8
Target the same APIs you use in the browser: fetch, Response, Request, Streams, and more
Use bajillions of packages on NPM to solve problems (or create new problems…)

Edge API spot graphic — Lightning fast Edge Libraries
Deliver http requests with unbelievable low latency using fly.cache
Modify content on every request: rewrite html, resize images, compress assets, etc.

Hostname API spot graphic — Powerful hostname API
Add unlimited hostnames with a simple `POST`
Give all your customers their own hostname with SSL
Wildcard hostnames (soon)

Development environment spot graphic — Full development environment
Develop, run, and test locally using fly deploy/test
Staging and production environments
Build a proper continuous integration pipeline

Optimize images

Remix everything

Prerender for speed

Modern JavaScript

Lightning fast Edge Libraries

Powerful hostname API

Full development environment