For years, "adding AI to your web app" meant the same thing: sign up for an API key, wire up a backend proxy so you don't leak that key to the browser, meter your token usage, handle rate limits, and pray your bill doesn't explode when a feature goes viral. Every summary, every classification, every bit of generated text was a round-trip to someone else's data center.
Chrome is quietly changing that. A family of built-in AI APIs now ships a language model — Google's Gemini Nano — inside the browser. Your JavaScript can summarize an article, translate a comment, or generate structured data from an image without a single network call to an inference server. No API key. No backend. No per-token bill. And because the model runs on-device, the user's data never leaves their machine.
In this article, I will walk you through what these APIs are, how to use them safely, and two hands-on examples: summarizing user reviews, and turning a product photo into structured JSON with the Prompt API.
The lineup: task APIs vs. the Prompt API
Chrome's built-in AI comes in two flavors.
