Introduction

Extension.dev is the hosted platform that builds a browser extension for every browser it declares, serves shareable previews, promotes releases through channels, and submits to the stores. Reach for it when more than one person, browser or store is involved in shipping your extension.

Quick start

npx extension@latest create my-extension --template=init
cd my-extension
gh repo create my-extension --private --source=. --push

Open extension.dev/new, sign in with GitHub, and pick the repository. The platform analyzes it and queues a build for every browser the manifest declares. The Quickstart walks every step.

How it works

Two halves. Extension.dev sponsors Extension.js, the open source framework it builds on. Extension.js is create, dev, build, local debugging and the agent bridge. It runs on your machine, needs no account, and is documented at extension.js.org, not here.

Where the platform begins. The platform begins where a token or a session is minted. A thing that works without a workspace is documented on the framework site. A thing that needs a sign-in, an access token or a share link is documented here.

	Extension.js	Extension.dev
What it is	Open source framework and CLI	Hosted platform
Where it runs	Your machine and your CI	The platform's infrastructure
What it does	Compiles, runs and bundles the extension	Builds, promotes releases, shares previews, submits to stores
Docs	extension.js.org	This site

One compiler. Every platform build runs the Extension.js compiler. The platform starts to matter when more than one person, browser or store is involved.

Builds for every browser from one commit. A project builds Chrome, Firefox and Edge artifacts from the same commit, in a build repository the platform owns, so build minutes never burn on your account. Safari builds the same way on a paid plan. See Projects.

Release channels and environments. Every build carries an environment stamp, production or staging. A build promotes through channels, and each channel is bound to one of the two. See Environments and Channels.

Shared previews. A build renders in a browser emulator behind a link. The person who opens it installs nothing. See Share an unpublished build for review.

Store submissions. Chrome Web Store, Firefox Add-ons, Microsoft Edge Add-ons and Safari credentials are entered once per project and reused by every submission. Chrome, Edge and Firefox submissions run on both plans. Safari builds and App Store submissions go together, and they need a paid plan. See Publishing and extension.dev/pricing.

Sign in. The button sits at the right of the nav bar on extension.dev. From a marketing page it lands you in the console, which is the projects surface. From /new or /import it returns you to the page you were on, because those two pages need the session where you stand.

While sign-up is closed. The front door's Create a new extension menu offers Templates, Themes and Subscribe, and never /new. The More from the platform menu beside it lists Code, Inspect, About and founder news.

Reference

Surface	Use it for	Guide
console.extension.dev	Projects, builds, releases, store submissions, settings	Projects
extension.dev/new	Choose a template, or connect a GitHub repository	Quickstart
extension.dev/import	Turn a repository, a template or a generated artifact into a project	Import
templates.extension.dev	The full catalog, each template running live in the page	Templates
themes.extension.dev	Build a browser theme against Chrome's own color math	Theme builder
preview.extension.dev	The door a shared build link opens on	Share a build for review
<workspace>.extension.dev	The public page for a released build	Public build pages
The HTTP API	Builds, promotes and store submissions from CI or a terminal	HTTP API
@extension.dev/mcp	The same verbs from a coding agent	MCP server
@extension.dev/skill	Teaching the agent when to use which one	Agent skill

When it fails

• You are looking for create, dev, build, or hot reload. That is the framework. The docs are at extension.js.org.
• You signed in and the console is empty. A new account starts with a workspace and no projects. Create one from extension.dev/new or connect a repository through Import. If you never reached the console at all, read the next entry first.
• Sign-in ended on /subscribe instead of the console. Sign-in is gated during the alpha. An account that is not on the invite list gets no session and lands on /subscribe, which explains why. The console was never opened.
• You cannot tell which site documents a feature. Ask whether it needs a session or a token. No: the framework site. Yes: this one.

Next

• Quickstart to get a project building in minutes
• Projects to understand what a project owns
• Import to connect an extension you already have