// 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>
# pip install openai
from openai import OpenAI
client = OpenAI(
base_url="https://api.puter.com/puterai/openai/v1/",
api_key="YOUR_PUTER_AUTH_TOKEN",
)
response = client.chat.completions.create(
model="x-ai/grok-4-fast",
messages=[
{"role": "user", "content": "Explain quantum computing in simple terms"}
],
)
print(response.choices[0].message.content)
curl https://api.puter.com/puterai/openai/v1/chat/completions \
-H "Content-Type: application/json" \
-H "Authorization: Bearer YOUR_PUTER_AUTH_TOKEN" \
-d '{
"model": "x-ai/grok-4-fast",
"messages": [
{"role": "user", "content": "Explain quantum computing in simple terms"}
]
}'
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 2M
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
Model Playground
Try Grok 4 Fast instantly in your browser.
This playground uses the Puter.js AI API — no API keys or setup required.
Benchmarks
How Grok 4 Fast performs on standard evaluations.
| Benchmark | Score |
|---|---|
| GPQA Diamond Graduate-level science Q&A | 60.6% |
| Humanity's Last Exam Cross-domain reasoning | 5.0% |
| LiveCodeBench Recent coding problems | 40.1% |
| SciCode Scientific programming | 32.9% |
| AIME 2025 Advanced math exam | 41.3% |
| IFBench Instruction following | 37.7% |
| LCR Long-context reasoning | 20.0% |
| Terminal-Bench Hard Agentic terminal tasks | 12.1% |
| τ²-Bench Tool use / agents | 63.7% |
Scores sourced from Artificial Analysis.
Find other xAI models →
Grok 4.5
Grok 4.5 is xAI's flagship mixture-of-experts model, trained jointly with Cursor on trillions of tokens of real coding sessions alongside STEM, research, and knowledge-work data. Elon Musk described it as an Opus-class model, faster and more token-efficient at a lower cost than comparable frontier models. It is tuned for coding, including Rust and C/C++, and for multi-step agentic workflows. It also handles finance and legal work, and can build multi-sheet Excel models with live web research, design diagrams in PowerPoint, and write structured documents in Word. Reasoning effort is configurable as low, medium, or high, with high as the default. The model accepts text and image input, supports a 500,000 token context window, and includes native tool calling. At $2 per million input tokens and $6 per million output tokens, it suits developers building coding agents and knowledge-work tools who need frontier-level capability without paying Opus-class pricing.
ImageGrok Imagine Image
Grok Imagine Image is xAI's standard text-to-image generation model, built on Aurora — an autoregressive Mixture-of-Experts architecture trained on billions of text-image pairs. It accepts text prompts and optional reference images as input, producing up to 10 images per request at 1K (1024×1024) or 2K (2048×2048) resolution across 13 aspect ratios. Output formats include JPEG, PNG, and WebP. The model is noted for strong instruction following, handling style transfer, object addition or removal, and multi-reference composition through natural language alone. It generates images quickly, making it practical for high-volume pipelines. Best suited for product mockups, marketing visuals, social media graphics, and concept art prototyping where speed and prompt adherence matter. A higher-quality variant, Grok Imagine Image Pro, is available when output fidelity is the priority.
ImageGrok Imagine Image (Quality)
Grok Imagine Image (Quality) is xAI's high-fidelity text-to-image generation model, built on the Aurora autoregressive Mixture-of-Experts architecture rather than a diffusion backbone. It targets applications where output quality is the priority over speed — delivering more natural lighting, richer textures, and cinematic consistency compared to standard-tier image models. Text rendering in generated images is notably legible across multiple languages, addressing a historically weak area for generative image models. The API supports 1K and 2K resolutions, 13 aspect ratios, and JPEG, PNG, and WebP outputs. Up to four image candidates can be generated per request. At $0.05 per image, it is well suited for product visuals, marketing assets, brand imagery, and creative workflows that require production-ready quality.
Frequently Asked Questions
You can access Grok 4 Fast by xAI through Puter.js AI API. Include the library in your web app or Node.js project and start making calls with just a few lines of JavaScript — no backend and no configuration required. You can also use it with Python or cURL via Puter's OpenAI-compatible API.
Yes, it is free if you're using it through Puter.js. With the User-Pays Model, you can add Grok 4 Fast to your app at no cost — your users pay for their own AI usage directly, making it completely free for you as a developer.
| Price per 1M tokens | |
|---|---|
| Input | $0.2 |
| Output | $0.5 |
Grok 4 Fast was created by xAI and released on Sep 19, 2025.
Grok 4 Fast supports a context window of 2M tokens. For reference, that is roughly equivalent to 4,000 pages of text.
Grok 4 Fast can generate up to 2M tokens in a single response.
Grok 4 Fast has a knowledge cutoff date of Jul 2025. This means the model was trained on data available up to that date.
Grok 4 Fast accepts the following input types: text, image. It produces: text.
Yes, 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.
Grok 4 Fast scores 16.5 on the Artificial Analysis Intelligence Index, outperforming 53% of tracked models. On math, it scores 41.3 (outperforms 42% of models).
Yes — the 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 Grok 4 Fast to your app without worrying about API keys or setup.
Read the Docs View Tutorials