Chrome Extension Built-in AI APIs — Developer Guide

4 min read

Chrome Built-in AI APIs

Introduction

Chrome ships on-device AI through chrome.ai. These APIs run locally on the user’s machine, meaning no data leaves the device. This is a game changer for extensions needing AI without external servers.

The on-device approach trades some accuracy for privacy and latency.

Checking API Availability

async function checkAIAvailability() {
  if (!('ai' in chrome)) return { available: false };
  const capabilities = await chrome.ai.canCreatePromptSession();
  return { available: capabilities === 'readily' };
}

Returns ‘readily’, ‘after-download’, or ‘no’.

Prompt API

Foundation for on-device language models. Supports sessions, streaming, parameters.

Sessions

Create a session to maintain context:

const session = await chrome.ai.createPromptSession({
  context: 'You are a helpful coding assistant.'
});
const response = await session.prompt('How do I filter an array?');
await session.destroy();

Streaming

For immediate feedback:

const stream = session.promptStreaming('Explain async/await');
for await (const chunk of stream) { updateUI(chunk); }

Temperature

Control randomness:

const response = await session.prompt('Write a function', {
  temperature: 0.2, maxTokens: 500
});

Use 0 for facts, 0.7-0.9 for creative tasks.

Summarizer API

Condenses text into summaries.

Types

const summarizer = await chrome.ai.createSummarizer({
  type: 'key-points', length: 'medium'
});
const summary = await summarizer.summarize(longText);

Length: ‘short’, ‘medium’, ‘long’. Content scripts can extract page text directly.

Writer API

Composes new text:

const writer = await chrome.ai.createWriter({ tone: 'formal' });
const drafted = await writer.write('Write a rejection email');

Tone: ‘formal’, ‘casual’, ‘persuasive’, ‘neutral’.

Rewriter API

Transforms existing text:

const rewriter = await chrome.ai.createRewriter({ tone: 'casual' });
const rewritten = await rewriter.rewrite(formalText);

Translation API

On-device translation:

const translator = await chrome.ai.createTranslator({
  sourceLanguage: 'en', targetLanguage: 'es'
});
const translated = await translator.translate('Hello');

Use BCP-47 codes. Not all pairs available.

Language Detection

const detector = await chrome.ai.createLanguageDetector();
const result = await detector.detect('Bonjour');
console.log(result.detectedLanguage); // 'fr'

Extension Context

Service Worker

Long-lived sessions in background. Watch for termination.

Content Scripts

Analyze page content directly. Good for summarizing articles.

Short lifetime. Create sessions in service worker, pass results via message passing:

chrome.runtime.onMessage.addListener((msg, sender, sendResponse) => {
  if (msg.type === 'summarize') {
    summarizeInBackground(msg.content).then(sendResponse);
    return true;
  }
});

Fallback Patterns

Build graceful degradation:

async function smartSummarize(text) {
  if ('ai' in chrome && await chrome.ai.canCreateSummarizer() === 'readily') {
    return (await chrome.ai.createSummarizer()).summarize(text);
  }
  return fallbackSummarize(text);
}

Consider external APIs, keyword extraction, or clear error messaging.

Privacy Benefits

On-device AI means sensitive data never leaves the machine. Critical for extensions handling passwords, messages, financial data, health records, or proprietary content.

Extensions offer AI features while maintaining trust. No data sent to third parties. No network calls for AI.

This privacy-first approach aligns with Chrome’s direction and user expectations. Extensions using on-device AI can market themselves as privacy-respecting alternatives to cloud solutions.

For more advanced AI integration patterns in Chrome extensions, check out the guides at zovo.one.

Part of the Chrome Extension Guide by theluckystrike. Built at zovo.one.

← Previous cheatsheet Next → chrome-extension-api-mocking