xAI: Grok 4 Fast API

Access xAI: Grok 4 Fast from xAI using Puter.js AI API.

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Model Card

Grok 4 Fast is an optimized variant delivering performance similar to Grok 4 but using 40% fewer thinking tokens with a massive 2 million token context window. It offers up to 64x cost reduction versus early frontier models like OpenAI's o3.

Context Window N/A

tokens

Max Output 2M

tokens

Input Cost $0.2

per million tokens

Output Cost $0.5

per million tokens

Input text, image

modalities

Tool Use Yes

 

Knowledge Cutoff Jul 2025

 

Release Date Sep 19, 2025

 

API Usage Example

Add xAI: Grok 4 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-4-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-4-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 xAI: Grok 4 Fast API about?

The xAI: Grok 4 Fast API gives you access to xAI's chat model through Puter.js. With just a few lines of JavaScript, you can integrate xAI: Grok 4 Fast into any web app or Node.js project — no API keys, no backend, and no configuration required.

Who created xAI: Grok 4 Fast?

xAI: Grok 4 Fast was created by xAI and released on Sep 19, 2025.

What is the max output length of xAI: Grok 4 Fast?

xAI: Grok 4 Fast can generate up to 2M tokens in a single response.

What is the knowledge cutoff of xAI: Grok 4 Fast?

xAI: Grok 4 Fast has a knowledge cutoff date of Jul 2025. This means the model was trained on data available up to that date.

What types of input can xAI: Grok 4 Fast process?

xAI: Grok 4 Fast accepts the following input types: text, image. It produces: text.

Does xAI: Grok 4 Fast support tool use (function calling)?

Yes, xAI: Grok 4 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 xAI: Grok 4 Fast API is available through the User-Pays Model. As a developer, you can add the xAI: Grok 4 Fast API to your app for free — your users pay for their own AI costs directly.
Price per 1M tokens
Input$0.2
Output$0.5
How do I access the xAI: Grok 4 Fast API?

You can access the xAI: Grok 4 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 xAI: Grok 4 Fast API work with React / Vue / Vanilla JS / Node / etc.?

Yes — the xAI: Grok 4 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 xAI: Grok 4 Fast to your app without worrying about API keys or setup.

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