Grok 4 Fast
Grok 4 Fast is a text and image understanding model from X.ai with a 2,000,000-token context window.
X.aiFast large-context text and vision model
Grok 4 Fast is a large language model developed by X.ai, the AI division of xAI founded by Elon Musk. It supports both text generation and image inputs, and is built around a 2,000,000-token context window, allowing it to process and reason over very long documents or multi-turn conversations in a single request. The model was made available in September 2025 and is offered as a first-party model on platforms that integrate the xAI API.
Grok 4 Fast is designed for use cases that require handling large volumes of text or images efficiently, such as document analysis, extended coding sessions, and multi-modal reasoning tasks. Its large context capacity makes it particularly suited for workflows where retaining information across long inputs is important, such as summarizing lengthy reports or analyzing large codebases. Developers can access it through MindStudio without managing separate API keys or infrastructure.
What Grok 4 Fast supports
Large Context Window
Processes up to 2,000,000 tokens in a single request, enabling analysis of very long documents, codebases, or extended conversations without truncation.
Text Generation
Generates coherent, contextually grounded text responses for tasks including summarization, drafting, question answering, and instruction following.
Image Understanding
Accepts image inputs alongside text prompts, supporting tasks such as visual question answering, image description, and multi-modal reasoning.
Long Document Analysis
Handles multi-document or multi-file inputs within its 2M-token limit, making it usable for legal review, research synthesis, and report analysis.
Code Assistance
Supports code generation, explanation, and debugging across common programming languages within extended multi-file context.
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Get Started FreeBenchmark scores
Scores represent accuracy — the percentage of questions answered correctly on each test.
| Benchmark | What it tests | Score |
|---|---|---|
| MMLU-Pro | Expert knowledge across 14 academic disciplines | 73.0% |
| GPQA Diamond | PhD-level science questions (biology, physics, chemistry) | 60.6% |
| LiveCodeBench | Real-world coding tasks from recent competitions | 40.1% |
| HLE | Questions that challenge frontier models across many domains | 5.0% |
| SciCode | Scientific research coding and numerical methods | 32.9% |
Common questions about Grok 4 Fast
What is the context window size for Grok 4 Fast?
Grok 4 Fast has a context window of 2,000,000 tokens, which is also the maximum response size. This allows it to handle very long inputs and outputs in a single request.
Does Grok 4 Fast support image inputs?
Yes. The model supports image inputs in addition to text, enabling multi-modal tasks such as image description and visual question answering.
Who publishes Grok 4 Fast?
Grok 4 Fast is published by X.ai (xAI) and is available as a first-party model. It was added to MindStudio in September 2025.
What is the pricing for Grok 4 Fast?
Pricing information for Grok 4 Fast is not published in the available metadata. Check the MindStudio platform or the xAI website for current pricing details.
What is the knowledge cutoff for Grok 4 Fast?
A specific knowledge cutoff date is not listed in the available metadata for Grok 4 Fast. Refer to xAI's official documentation for the most accurate training data cutoff information.
What people think about Grok 4 Fast
Community discussions around Grok 4 Fast have focused on its benchmark performance and token efficiency, with users noting its scores on AIME, HMMT, and LiveCodeBench as concrete evidence of its reasoning capabilities. The search-enabled variant's first-place ranking on LMArena's Search Arena has also drawn attention in AI-focused communities.
Some threads in the r/singularity community have broadened into discussions about general progress on benchmarks like ARC-AGI 2, which are not directly tied to Grok 4 Fast but reflect the wider context in which the model is being evaluated. Developers appear most interested in the model's cost-to-performance ratio and its suitability for agentic and long-context use cases.
xAI releases details and performance benchmarks for Grok 4 Fast
ARC-AGI 2 is Solved
Poetiq Achieves SOTA on ARC-AGI 2 Public Eval
Documentation & links
Parameters & options
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