Puter.js gives you access to auth, cloud storage, databases, and AI (Claude, GPT, Gemini, and 500+ other models) with no API keys and no infrastructure setup. The entire library is a single <script> tag or the @heyputer/puter.js npm module.
This is also what makes Puter.js work so well as the backend for AI-generated apps. There is nothing to configure: no keys to obtain, no servers to provision, no SDK to initialize. AI coding tools and platforms like Claude Code, Codex, OpenCode, Lovable, and Replit can generate complete, working apps in a single shot with Puter.js. The API is small and consistent enough for language models to use correctly, and the full reference is published as llms.txt so AI tools can read it in one request.
<script src="https://js.puter.com/v2/"></script>
Additionally, with Puter.js, you as the developer pay nothing since each user of your app covers their own Cloud and AI usage. Whether your app has 1 user or 1 million users, it costs you zero to run. Puter.js gives you infinitely scalable infrastructure, completely free.
Puter.js is powered by Puter, the open-source cloud operating system with a heavy focus on privacy. Puter does not use tracking technologies and does not monetize or even collect personal information.
<html>
<body>
<script src="https://js.puter.com/v2/"></script>
<script>
// Create a new file called "hello.txt" containing "Hello, world!"
puter.fs.write('hello.txt', 'Hello, world!').then((file) => {
puter.print(`File written successfully at: ${file.path}`);
})
</script>
</body>
</html>
Read a file from the cloud
<html>
<body>
<script src="https://js.puter.com/v2/"></script>
<script>
(async () => {
// (1) Create a random text file
let filename = puter.randName() + ".txt";
await puter.fs.write(filename, "Hello world! I'm a file!");
puter.print(`"${filename}" created<br>`);
// (2) Read the file and print its contents
let blob = await puter.fs.read(filename);
let content = await blob.text();
puter.print(`"${filename}" read (content: "${content}")<br>`);
})();
</script>
</body>
</html>
<html>
<body>
<script src="https://js.puter.com/v2/"></script>
<script>
// (1) Save user preference
puter.kv.set('userPreference', 'darkMode').then(() => {
// (2) Get user preference
puter.kv.get('userPreference').then(value => {
puter.print(`User preference: ${value}`);
});
})
</script>
</body>
</html>
<html>
<body>
<script src="https://js.puter.com/v2/"></script>
<script>
// Chat with GPT-5.4 nano
puter.ai.chat(`What is life?`, { model: "gpt-5.4-nano" }).then(puter.print);
</script>
</body>
</html>
Image Analysis
<html>
<body>
<script src="https://js.puter.com/v2/"></script>
<img src="https://assets.puter.site/doge.jpeg" style="display:block;">
<script>
puter.ai
.chat(`What do you see?`, `https://assets.puter.site/doge.jpeg`, {
model: "gpt-5.4-nano",
})
.then(puter.print);
</script>
</body>
</html>
Generate an image of a cat using AI
<html>
<body>
<script src="https://js.puter.com/v2/"></script>
<script>
// Generate an image of a cat using the default model and quality. Please note that testMode is set to true so that you can test this code without using up API credits.
puter.ai.txt2img('A picture of a cat.', true).then((image)=>{
document.body.appendChild(image);
});
</script>
</body>
</html>
Stream the response
<html>
<body>
<script src="https://js.puter.com/v2/"></script>
<script>
(async () => {
const resp = await puter.ai.chat('Tell me in detail what Rick and Morty is all about.', {model: 'gemini-3.1-flash-lite', stream: true });
for await ( const part of resp ) puter.print(part?.text?.replaceAll('\n', '<br>'));
})();
</script>
</body>
</html>
<html>
<body>
<script src="https://js.puter.com/v2/"></script>
<script>
(async () => {
// (1) Create a random directory
let dirName = puter.randName();
await puter.fs.mkdir(dirName)
// (2) Create 'index.html' in the directory with the contents "Hello, world!"
await puter.fs.write(`${dirName}/index.html`, '<h1>Hello, world!</h1>');
// (3) Host the directory under a random subdomain
let subdomain = puter.randName();
const site = await puter.hosting.create(subdomain, dirName)
puter.print(`Website hosted at: <a href="https://${site.subdomain}.puter.site" target="_blank">https://${site.subdomain}.puter.site</a>`);
})();
</script>
</body>
</html>
<html>
<body>
<script src="https://js.puter.com/v2/"></script>
<button id="sign-in">Sign in</button>
<script>
// Because signIn() opens a popup window, it must be called from a user action.
document.getElementById('sign-in').addEventListener('click', async () => {
// signIn() will resolve when the user has signed in.
await puter.auth.signIn().then((res) => {
puter.print('Signed in<br>' + JSON.stringify(res));
});
});
</script>
</body>
</html>
<html>
<body>
<script src="https://js.puter.com/v2/"></script>
<script>
(async () => {
// Send a GET request to example.com
const request = await puter.net.fetch("https://example.com");
// Get the response body as text
const body = await request.text();
// Print the body as a code block
puter.print(body, { code: true });
})()
</script>
</body>
</html>