Grok 3 Fast API

Access Grok 3 Fast from xAI using Puter.js AI API.

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Model Card

Grok 3 Fast is a latency-optimized variant of Grok 3 using the same underlying model but served on faster infrastructure. It delivers quicker response times for latency-sensitive applications while maintaining equivalent reasoning quality and 131K context window.

Context Window 131K

tokens

Max Output 131K

tokens

Input Cost $5

per million tokens

Output Cost $25

per million tokens

Input text

modalities

Tool Use Yes

 

Knowledge Cutoff Nov 2024

 

Release Date Feb 17, 2025

 

API Usage Example

Add Grok 3 Fast to your app with just a few lines of code.
No API keys, no backend, no configuration required.

// npm install @heyputer/puter.js
import { puter } from '@heyputer/puter.js';

puter.ai.chat("Explain quantum computing in simple terms", {
    model: "x-ai/grok-3-fast"
}).then(response => {
    document.body.innerHTML = response.message.content;
});

<html>
<body>
    <script src="https://js.puter.com/v2/"></script>
    <script>
        puter.ai.chat("Explain quantum computing in simple terms", {
            model: "x-ai/grok-3-fast"
        }).then(response => {
            document.body.innerHTML = response.message.content;
        });
    </script>
</body>
</html>

View full documentation →

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Frequently Asked Questions

What is this Grok 3 Fast API about?

The Grok 3 Fast API gives you access to xAI's chat model through Puter.js. With just a few lines of JavaScript, you can integrate Grok 3 Fast into any web app or Node.js project — no API keys, no backend, and no configuration required.

Who created Grok 3 Fast?

Grok 3 Fast was created by xAI and released on Feb 17, 2025.

What is the context window of Grok 3 Fast?

Grok 3 Fast supports a context window of 131K tokens. For reference, that is roughly equivalent to 262 pages of text.

What is the max output length of Grok 3 Fast?

Grok 3 Fast can generate up to 131K tokens in a single response.

What is the knowledge cutoff of Grok 3 Fast?

Grok 3 Fast has a knowledge cutoff date of Nov 2024. This means the model was trained on data available up to that date.

What types of input can Grok 3 Fast process?

Grok 3 Fast accepts the following input types: text. It produces: text.

Does Grok 3 Fast support tool use (function calling)?

Yes, Grok 3 Fast supports tool use (function calling), allowing it to interact with external tools, APIs, and data sources as part of its response flow.

How much does it cost?
The Grok 3 Fast API is available through the User-Pays Model. As a developer, you can add the Grok 3 Fast API to your app for free — your users pay for their own AI costs directly.
Price per 1M tokens
Input$5
Output$25
How do I access the Grok 3 Fast API?

You can access the Grok 3 Fast API with just a few lines of JavaScript — no API keys, no backend, and no configuration required. Include the Puter.js library in your project and start making calls right away. For more details, check out our documentation.

Does the Grok 3 Fast API work with React / Vue / Vanilla JS / Node / etc.?

Yes — the Grok 3 Fast API works with any JavaScript framework, Node.js, or plain HTML through Puter.js. Just include the library and start building. See the documentation for more details.

Get started with Puter.js

Add Grok 3 Fast to your app without worrying about API keys or setup.

Read the Docs View Tutorials