An open spec & SDK for creating web apps that agents can use.
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Web Applets is a Mozilla Builders project.
Web Applets is an open specification for building software that both humans and AI can understand and use together. Instead of forcing AI to operate traditional point-and-click apps built for humans, Web Applets creates a new kind of web software designed for human-AI collaboration.
Unternet is building a new, intelligent user agent that can do things for you across the web. As part of that effort, we needed a way to actuate an embedded web app. You can do this with a computer use model, but for many use cases it's not suitable to point and click around in a virtual browser. Why make a computer talk to another computer via a clumsy web interface when they can just talk directly?
Web Applets lets you define a simple, computer-readable API for a web app running in a browser, webview, or iframe. You can send it actions as JSON objects, which an LLM can easily create (see OpenAI's structured JSON endpoint), and they can update their UI instantly in-place. Plus, you can expose the internal state of the applets to the model so you can do cool stuff like chat to a map.
We wanted anyone to be able to build these actions into their own third-party applets and distribute them. So, we extended the web & made it available to everyone!
Create a new web app using our CLI:
npx @web-applets/createInside the generated folder, you'll find a basic web app setup:
public/manifest.json: A web app manifest, useful when publishing your applet, adding icons, etc.index.html: Much like a website, this holds the main page for your appletsrc/main.ts: Declares functions that respond to each action, and a render function that updates the view based on state
Want to use React? Svelte? Vue? – No problem, just install the dependencies and create an app the way you normally would in a website. So long as you're receiving the action events, it will all just work.
Now let's build out a basic web applet that will say hello when we send it an action:
index.html:
<!DOCTYPE html>
<html lang="en">
<script src="./main.js" type="module"></script>
<body>
Hello! <span id="name">whoever you are</span>.
</body>
</html>Let's add some Web Applets functionality, so this can respond to a set_name action:
main.js:
import { applets } from '@web-applets/sdk';
const context = applets.getContext();
// Define a 'set_name' action, and make it update the shared data object with the new name
context.defineAction('set_name', {
params: {
name: {
type: 'string',
description: 'The name of the person to be greeted.',
},
},
handler: ({ name }) => {
context.data = { name }
},
});
// Whenever the data is updated, update the view
context.ondata = () => {
const nameElement = document.getElementById('name');
if (nameElement) {
nameElement.innerText = context.data.name;
}
};To test out this applet, first start the dev server with npm run dev, and take note of the dev server URL. Then, fire up the Web Applets inspector by running npx @web-applets/inspector, and enter the dev URL into the URL bar up the top.
You can build this applet, by running npm run build, and host it on any static site host. This applet will now work in any environment where the SDK is installed.
In order to run, web applets need to be embedded in an environment that supports the Web Applets protocol. This might look like a browser (email me if you're interested!), or an electron app with <webview> tags, or sometthing as simple as a web-based AI chat client using iframes.
First, install & import the applets SDK in your client app:
npm install @web-applets/sdkimport { applets } from '@web-applets/sdk';Now you can import your applets from wherever they're being served from (note – you can also host them locally, or anywhere on the web):
const applet = await applets.load('https://applets.unternet.co/maps');
applet.ondata = (e) => console.log(e.data);
applet.dispatchAction('set_name', { name: 'Web Applets' }); // console.log: { name: "Ada Lovelace" }The above applet is actually running headless, but we can get it to display by attaching it to a container. For the loading step, instead run:
const container = document.createElement('iframe');
document.body.appendChild(container);
const applet = await applets.load(`/helloworld.applet`, container);To load pre-existing saved data into an applet, simply set the data property:
applet.data = { name: 'Ada Lovelace' }; // console.log: { name: "Ada Lovelace" }This is a community project, and we're open to community members discussing the project direction, and submitting code!
To join the conversation, visit the Applets mailing list here. You can also find more about the company that's kicking off this work at unternet.co
Built by Unternet.