Artificial intelligence has evolved from a futuristic promise into a tangible and powerful tool in our daily lives as developers. Until recently, integrating AI into our web applications meant relying on external servers, dealing with latency, and managing costs. But what if I told you that the game is about to change dramatically? Google has given us a new and powerful tool: the Prompt API, which allows us to run AI models, like Gemini Nano, directly in the user’s browser.

I’ve been experimenting with this API recently, and the feeling is electrifying. We are facing a paradigm shift that not only improves performance but also addresses key concerns like privacy and personalization. Join me as I break down why I believe this API is so revolutionary.

Why is it revolutionary?

The true revolution of the Prompt API lies in three fundamental pillars:

1. Privacy by Design: By running the AI model on the client, the user’s data never leaves their device. This is a massive change. Imagine being able to offer intelligent features without the user having to worry about how their personal information is handled in the cloud. This not only builds trust but also greatly simplifies compliance with privacy regulations.

2. Zero Latency: Communicating with an external server inevitably introduces a delay. With the Prompt API, inference happens locally, resulting in almost instantaneous responses. This is crucial for creating fluid and interactive user experiences that feel natural, not like you’re waiting for a response from a distant server.

3. Offline Availability: Once the model has been downloaded, the application can continue to function without an internet connection. This opens the door to a new type of intelligent web application that is robust and always available, regardless of the quality of the user’s connection.

First Steps: A Simple Example

Before we dive into more complex use cases, let’s see how simple it is to get started. The first thing is to check if the user’s browser can run the model.

// Check if the API is available
const availability = await window.ai.getAvailability();

if (availability === "available") {
  console.log("AI is ready to use!");
} else {
  console.log("AI is not available on this device.");
}

If it’s available, we can create a session and send it a prompt. It’s that easy!

if (availability === "available") {
  // Create an inference session
  const session = await window.ai.createSession();

  // Send a prompt and wait for the full response
  const response = await session.prompt("Write me a short poem about code.");
  console.log(response);

  // Don't forget to destroy the session to free up resources
  session.destroy();
}

This simple code snippet already shows us the power we have at our fingertips.

Use Cases Where This API Would Shine

The possibilities are enormous, but here are a few ideas where the Prompt API could have an immediate and significant impact:

• Intelligent Writing Assistants: Imagine a text editor that not only corrects your grammar but also helps you rephrase sentences, adjust the tone, or even generate complete drafts of emails or articles, all in real-time and without sending your drafts to any server.

• Content Classification and Organization: A news site or blog could use the API to automatically classify articles into relevant categories for the user, allowing for the creation of personalized and dynamic feeds without needing backend logic.

• Client-Side Semantic Search: Instead of a simple keyword search, you could implement a search that understands the meaning behind the user’s query within the content of a page or a set of documents, offering much more accurate results.

• Audio Transcription and Image Description: The API has multimodal capabilities. You could allow users to record voice notes and transcribe them instantly, or upload an image and automatically generate descriptive alt text to improve accessibility.

Why Is This Important?

The Prompt API isn’t just a new feature; it’s a statement about the future of the web. It’s empowering us as developers to build the next generation of web applications: smarter, more private, and more user-centric.

By moving AI to the client, access to this technology is democratized. Large server infrastructures and high inference budgets are no longer required. Small developers and teams can now compete on a level playing field, creating innovative experiences that were previously reserved for large corporations.

Exploring the API in Depth: More Examples

The official documentation provides more advanced examples that are worth exploring.

Streaming Responses

For longer responses, we can display the result as it’s generated, improving the perception of speed.

const session = await window.ai.createSession();
const stream = session.promptStreaming(
  "Write me an extra-long poem about the universe"
);

for await (const chunk of stream) {
  // Append each chunk to your UI
  document.getElementById("poem-div").textContent += chunk;
}

Maintaining Context

Sessions remember previous interactions, allowing for fluid conversations.

const session = await window.ai.createSession({
  initialPrompts: [
    { role: "system", content: "You are a friendly and helpful assistant." },
  ],
});

let response1 = await session.prompt("What is the capital of Italy?");
console.log(response1); // "The capital of Italy is Rome."

let response2 = await session.prompt("And what language is spoken there?");
console.log(response2); // "The official language of Italy is Italian."

Structured Output with JSON

You can force the model to respond in a specific JSON format, which is incredibly useful for integrating the AI with other parts of your application.

const session = await window.ai.createSession();
const schema = { type: "boolean" };
const post = "Today I baked some ceramic mugs and they turned out great.";

const result = await session.prompt(`Is this post about ceramics?\n\n${post}`, {
  responseConstraint: schema,
});

console.log(JSON.parse(result)); // true

Conclusion: The Future is Local

My experience with the Prompt API has been revealing. It’s one of those technologies that makes you feel like you’re witnessing the beginning of something big. It gives us the tools to build a smarter, more privacy-respecting web, right from the browser.

I invite you to dive in, experiment, and think about how you can use this incredible capability in your own projects. The future of AI on the web is local, and it’s already here.