At Build 2025, we introduced the Prompt and Writing Assistance APIs in Microsoft Edge with the Phi-4-mini language model. Since then, we’ve heard from web developers, incorporated your feedback, and expanded Edge’s on-device AI capabilities with new models and APIs.

Today, we’re introducing three updates:

1. A developer preview of the pre-release Aion-1.0-Instruct small language model for early testing and feedback.
2. The Language Detector and Translator APIs in Edge 148, powered by on-device, task-specific models.
3. Experimental on-device speech recognition with the Web Speech API, available in Edge Canary and Dev channels.

Developer preview of Aion-1.0-Instruct

For the past year, the Prompt and Writing Assistance APIs have used Phi-4-mini, a highly capable 4B-parameter language model, in Edge. While it delivers strong text understanding, reasoning, and instruction-following for web scenarios, the model’s hardware requirements have limited its availability across devices.

Today, we’re introducing a developer preview of the pre-release Aion-1.0-Instruct small language model in Edge Canary and Dev channels. This language model is smaller, faster, and more efficient. It expands support to significantly more devices — including those with less capable GPUs and, through CPU-inference, devices without a GPU — while delivering strong quality for a wide range of web use-cases.

This preview allows you to evaluate Aion-1.0-Instruct in real-world web scenarios, test API interoperability, and provide feedback that will guide final optimizations, ahead of its planned open-source release on Hugging Face in July. To try out the model, explore the documentation for the Prompt API and Writing Assistance APIs, experiment with the playground samples, and share your feedback on GitHub.

Language Detector and Translator APIs in Edge 148

The Language Detector and Translator APIs enable websites and browser extensions to identify the language of text and translate between language pairs. These APIs are now available in Edge 148, powered by on-device, task-specific models built directly into the browser. They deliver fast, high-quality translation, support 145+ languages, and are optimized for translation workloads on the web.

You can use these APIs from JavaScript in your site or extension, gaining improved user privacy, network independence, and zero translation costs compared to cloud-based services.

In their simplest form, the Language Detector and Translator APIs can be used as shown:

// Create a Language Detector session.
const detector = await LanguageDetector.create();

// Detect the language of the text.
const results = await detector.detect(userText);

// Use the results.
for (const result of results) {
  // Show the full list of potential languages with their likelihood,
  // ranked from most likely to least likely.
  console.log(result.detectedLanguage, result.confidence);
}

// Create a Translator session.
const translator = await Translator.create({
  sourceLanguage: "es",
  targetLanguage: "en"
});

// Translate the text and wait for the translation to be done.
const translatedText = await translatorSession.translate(userText);

// Use the translation. 
console.log(translatedText);

To learn more, check out the documentation for the Language Detector API and Translator API, try our playground samples, and share your feedback in the Language Detector and Translator feedback issues on GitHub.

On-device speech recognition with the Web Speech API

The Web Speech API enables you to incorporate voice or audio input into websites and browser extensions. This API is typically backed by cloud-based services for speech recognition (speech-to-text) and synthesis (text-to-speech).

In the latest Edge Canary and Dev channels, we’re introducing a task-specific model that processes speech locally on the user’s device. This on-device implementation improves user privacy, reduces latency, and unlocks low-connectivity scenarios that require network independence.

Using the new on-device speech recognition capability requires only minor updates to your existing Web Speech API code, as shown:

// Create a SpeechRecognition instance.
const recognition = new SpeechRecognition();
recognition.lang = 'en-US';

// Use on-device speech recognition.
recognition.processLocally = true;

// Start speech recognition.
recognition.start();

To get started with on-device speech recognition, check out the documentation, try the playground demo, and share your feedback on GitHub.

Try it out and let us know

With the Aion-1.0-Instruct small language model, the new Language Detector and Translator APIs, and on-device speech recognition in Microsoft Edge, you can build AI-powered web experiences by leveraging models built into the browser, without relying on specialized hardware, cloud services, or domain-specific expertise.

We invite you to explore these capabilities, experiment with the new models, and tell us what you build. Your feedback will shape the next iteration of on-device AI in Microsoft Edge, and we’re excited to partner with you as we continue expanding what’s possible for AI on the web.