@localmode/chrome-ai

Zero-download, instant AI inference via Chrome's built-in Gemini Nano model. Part of the LocalMode ecosystem.

Features

• Zero model downloads — Gemini Nano ships with Chrome
• Zero bundle size impact — browser-native APIs
• Instant inference — no model loading delay
• Implements SummarizationModel, TranslationModel, and LanguageModel from @localmode/core
• Automatic fallback support — pair with @localmode/transformers, @localmode/webllm, @localmode/wllama, or @localmode/litert for non-Chrome browsers

Requirements

• Chrome 138+ on desktop (Windows 10+, macOS 13+, Linux, or ChromeOS on Chromebook Plus)
• 22 GB free disk space on the volume containing your Chrome profile (for the Gemini Nano model)
• Hardware: GPU with >4 GB VRAM, or CPU with 16 GB+ RAM and 4+ cores
• Not available on mobile (Android/iOS) or in Incognito mode
• Non-Chrome browsers need a fallback provider (e.g., @localmode/transformers)

Enabling Chrome AI

1. Navigate to chrome://flags/#optimization-guide-on-device-model → set to Enabled
2. Navigate to chrome://flags/#prompt-api-for-gemini-nano → set to Enabled
3. Restart Chrome
4. The Gemini Nano model downloads automatically in the background (~1.5 GB)
5. Verify in DevTools Console: await Summarizer.availability() should return "readily"

For the Summarizer API specifically, also enable chrome://flags/#summarization-api-for-gemini-nano → Enabled with Adaptation for higher-quality summaries via LoRA.

Installation

pnpm add @localmode/chrome-ai @localmode/core

Quick Start

import { generateText, summarize, translate } from '@localmode/core';
import { chromeAI } from '@localmode/chrome-ai';

// Summarize text (instant, no download)
const { summary } = await summarize({
  model: chromeAI.summarizer(),
  text: 'Long article text...',
});

// Translate text
const { translation } = await translate({
  model: chromeAI.translator({ targetLanguage: 'de' }),
  text: 'Hello, world!',
});

// Generate text with Gemini Nano via the Prompt API
const { text } = await generateText({
  model: chromeAI.languageModel({ systemPrompt: 'You are concise.' }),
  prompt: 'Explain TLS in one sentence.',
});

Fallback Pattern

import { summarize } from '@localmode/core';
import { chromeAI, isSummarizerAPISupported } from '@localmode/chrome-ai';
import { transformers } from '@localmode/transformers';

const model = isSummarizerAPISupported()
  ? chromeAI.summarizer()
  : transformers.summarizer('Xenova/distilbart-cnn-6-6');

const { summary } = await summarize({ model, text: 'Long article...' });

API

chromeAI.summarizer(settings?)

Creates a SummarizationModel using Chrome's Summarizer API.

| Setting | Type | Default | Description | |---------|------|---------|-------------| | type | 'key-points' \| 'tl;dr' \| 'teaser' \| 'headline' | 'tl;dr' | Summary type | | format | 'markdown' \| 'plain-text' | 'plain-text' | Output format | | length | 'short' \| 'medium' \| 'long' | 'medium' | Summary length | | sharedContext | string | — | Context shared across calls |

chromeAI.translator(settings?)

Creates a TranslationModel using Chrome's Translator API.

| Setting | Type | Default | Description | |---------|------|---------|-------------| | sourceLanguage | string | 'en' | Source language (BCP 47) | | targetLanguage | string | 'es' | Target language (BCP 47) |

chromeAI.languageModel(settings?)

Creates a LanguageModel using Chrome's Prompt API (Gemini Nano). Supports generateText(), streamText(), generateObject(), and the model-warmup protocol via warmUp() / isReady().

| Setting | Type | Default | Description | |---------|------|---------|-------------| | systemPrompt | string | — | Prepended to every session as initialPrompts[0] | | temperature | number | Chrome default | Sampling temperature (0–1) | | topK | number | Chrome default | Top-K sampling cutoff | | contextLength | number | 6144 | Soft documentation value for model.contextLength | | onProgress | (p: { loaded: number; total: number }) => void | — | Forwarded to monitor for Gemini Nano download progress |

import { generateText } from '@localmode/core';
import { chromeAI } from '@localmode/chrome-ai';

const { text } = await generateText({
  model: chromeAI.languageModel({ systemPrompt: 'You are concise.' }),
  prompt: 'Explain quantum tunnelling in one sentence.',
});

Lifecycle Methods

ChromeAILanguageModel exposes lifecycle methods for fine-grained control:

| Method | Returns | Description | |--------|---------|-------------| | warmUp() | Promise<void> | Pre-initialize the Gemini Nano session so the next doGenerate() / doStream() has zero creation latency. Pairs with useModelWarmup() from @localmode/react. | | isReady() | boolean | true once a session is cached on this instance; false otherwise. | | destroy() | void | Release the cached session and free resources. Idempotent. Subsequent calls recreate a fresh session. |

import { ChromeAILanguageModel } from '@localmode/chrome-ai';

const model = new ChromeAILanguageModel({
  systemPrompt: 'You are concise.',
  temperature: 0.3,
});

await model.warmUp();
console.log(model.isReady()); // true

// ... use model with generateText() / streamText() ...

model.destroy(); // release resources

See the Language Model docs for streaming, structured output, fallback chains, and the full error reference.

Feature Detection

import {
  isChromeAISupported,
  isPromptAPISupported,
  isSummarizerAPISupported,
  isTranslatorAPISupported,
} from '@localmode/chrome-ai';

if (isChromeAISupported()) { /* Chrome AI available */ }
if (isPromptAPISupported()) { /* Prompt API (LanguageModel) available */ }
if (isSummarizerAPISupported()) { /* Summarizer API available */ }
if (isTranslatorAPISupported()) { /* Translator API available */ }

Exported Types

The package exports TypeScript types for Chrome's built-in AI APIs:

| Type | Description | |------|-------------| | ChromeAIProvider | Provider interface with summarizer(), translator(), languageModel() | | ChromeAIProviderSettings | Provider-level configuration | | ChromeAILanguageModelSettings | Settings for languageModel() (systemPrompt, temperature, topK, etc.) | | ChromeAISummarizerSettings | Settings for summarizer() (type, format, length) | | ChromeAITranslatorSettings | Settings for translator() (sourceLanguage, targetLanguage) | | AILanguageModel | Chrome Prompt API session interface | | AILanguageModelAvailability | Availability status: 'available' \| 'downloadable' \| 'downloading' \| 'unavailable' | | AILanguageModelCreateOptions | Options for LanguageModel.create() | | AILanguageModelFactory | Chrome Prompt API factory (window.LanguageModel) | | AILanguageModelPromptOptions | Per-call options for prompt() / promptStreaming() | | AISummarizer | Chrome Summarizer API session interface | | AISummarizerFactory | Chrome Summarizer API factory | | AISummarizerCapabilities | Summarizer capability detection | | AISummarizerCreateOptions | Options for Summarizer.create() | | AITranslator | Chrome Translator API session interface | | AITranslatorFactory | Chrome Translator API factory | | AITranslatorCapabilities | Translator capability detection | | AITranslatorCreateOptions | Options for Translator.create() |

Implementation Classes

The implementation classes are exported for direct instantiation or advanced wiring:

| Class | Implements | |-------|------------| | ChromeAILanguageModel | LanguageModel from @localmode/core | | ChromeAISummarizer | SummarizationModel from @localmode/core | | ChromeAITranslator | TranslationModel from @localmode/core |

import { ChromeAILanguageModel } from '@localmode/chrome-ai';

// Direct instantiation (bypasses provider factory)
const model = new ChromeAILanguageModel({
  systemPrompt: 'You are helpful.',
  topK: 40,
});

Acknowledgments

This package is built on Chrome Built-in AI by Google — on-device AI APIs powered by Gemini Nano, enabling zero-download inference directly in Chrome.

License

MIT