This model is deprecated. We only continue performance benchmarking for the default 10k input token workload. Results for other workloads are historical and no longer updated.

SpaceXAI has launched a newer release, Grok 4.1 Fast. We suggest considering it instead.

SpaceXAI

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Grok 4 Fast

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Proprietary model

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Released September 2025

Grok 4 Fast (Reasoning) Intelligence, Performance & Price Analysis

Name: Intelligence
Creator: Artificial Analysis
License: https://artificialanalysis.ai/docs/legal/Terms-of-Use.pdf

Try it out API Provider Benchmarks

Intelligence

18*

Artificial Analysis Intelligence Index

* Estimated

Speed

N/A

Output tokens per second

Cost

In $0.20Out $0.50

N/A

Cost per Intelligence Index task

Verbosity

N/A

Output tokens from Intelligence Index

Grok 4 Fast (Reasoning) is above average in intelligence, but somewhat expensive when comparing to other models of similar price. The model supports text and image input, outputs text, and has a 2M tokens context window.

Grok 4 Fast (Reasoning) scores 18 on the Artificial Analysis Intelligence Index, placing it above average among comparable models (median: 13).

Pricing for Grok 4 Fast (Reasoning) is $0.20 per 1M input tokens (moderately priced, median: $0.25) and $0.50 per 1M output tokens (competitively priced, median: $0.87).

Reasoning	Yes This page shows the reasoning version of this model. A non-reasoning variant may also exist.
Input modality	Supports: text and image
Output modality	Supports: text
Context window	2M ~3000 A4 pages of size 12 Arial font

Metrics are compared against models of the same class:

Non-reasoning models → compared only with other non-reasoning models
Reasoning models → compared across both reasoning and non-reasoning
Open weights models → compared only with other open weights models of the same size class:

Tiny: ≤4B parameters
Small: 4B–40B parameters
Medium: 40B–150B parameters
Large: >150B parameters

Proprietary models → compared across proprietary and open weights models of the same price range, using a blended 3:1 input/output price ratio:

<$0.15 per 1M tokens
$0.15–$1 per 1M tokens
>$1 per 1M tokens

Intelligence

Artificial Analysis Intelligence Index · Higher is better

Speed

Output tokens per second · Higher is better

Cost per Task

Weighted average cost (USD) per Intelligence Index task · Lower is better

Intelligence

Artificial Analysis Intelligence Index

Artificial Analysis Intelligence Index v4.3.2 incorporates 10 evaluations: AA-Briefcase v1.1, GDPval-AA v2.1, AutomationBench-AA, Terminal-Bench 4.0, SciCode, Humanity's Last Exam, GDP.pdf, CritPt, AA-Omniscience, AA-LCR v1.1

No publicly available API

Estimate (independent evaluation forthcoming)

Artificial Analysis Intelligence Index v4.3.2 includes: AA-Briefcase v1.1, GDPval-AA v2.1, AutomationBench-AA, Terminal-Bench 4.0, SciCode, Humanity's Last Exam, GDP.pdf, CritPt, AA-Omniscience, AA-LCR v1.1. See Intelligence Index methodology for further details, including a breakdown of each evaluation and how we run them.

Artificial Analysis Intelligence Index by Open Weights / Proprietary

No publicly available API

Estimate (independent evaluation forthcoming)

Indicates whether the model weights are available. Models are labelled as 'Commercial Use Restricted' if commercial use is limited by conditions, and as 'Non-commercial' if the license prohibits commercial use.

Intelligence Index vs. Cost per Intelligence Index Task

Artificial Analysis Intelligence Index · Weighted average cost (USD) per Artificial Analysis Intelligence Index task

Most attractive quadrant

Pareto line

Weighted average cost per Intelligence Index task. Each evaluation’s cost is calculated from input, cache hit, cache write, reasoning, and answer token prices, divided by task count, and weighted by its Intelligence Index weight.

Benchmarks

Intelligence Evaluations

Intelligence evaluations measured independently by Artificial Analysis · Higher is better

No publicly available API

AA-Briefcase v1.1Updated

Agentic knowledge work, (Elo-500)/2000

AA-Omniscience Accuracy

Knowledge

AA-Omniscience Non-Hallucination Rate

1 - hallucination rate

AutomationBench-AA

Agentic SaaS workflows

GDPval-AA v2.1Updated

Agentic real-world work tasks, (Elo-500)/2000

Humanity's Last Exam

Reasoning & knowledge

GDP.pdf

Professional document reasoning, All-pass

Terminal-Bench 4.0

Agentic coding & terminal use

AA-LCR v1.1

Long context reasoning

SciCodeUnder review

Coding

CritPtUnder review

Physics reasoning

Terminal-Bench-Science 0.1New

Agentic scientific research workflows in a terminal

FrontierCode 1.1New

Agentic software engineering in open-source repositories

AA-AnalystAgent

Quantitative analysis on spreadsheets & documents

Harvey LAB-AA v1.1Updated

Legal agentic work, Hallucination-Gated All-Pass Rate

EnterpriseOps-Gym-AA

Agentic business operations

ITBench-AA

Kubernetes incident root-cause analysis

MLCR-AA

Medical long context reasoning

MMMU-Pro

Visual reasoning

While model intelligence generally translates across use cases, specific evaluations may be more relevant for certain use cases.

AA-Omniscience

AA-Omniscience Index

AA-Omniscience Index (higher is better) measures knowledge reliability and hallucination. It rewards correct answers, penalizes hallucinations, and has no penalty for refusing to answer. Scores range from -100 to 100, where 0 means as many correct as incorrect answers, and negative scores mean more incorrect than correct.

No publicly available API

Intelligence Index Comparisons

Intelligence Index vs. Cost per Intelligence Index Task

Artificial Analysis Intelligence Index · Weighted average cost (USD) per Artificial Analysis Intelligence Index task

Most attractive quadrant

Pareto line

Cost

Cost per Intelligence Index Task

Weighted average cost (USD) per Artificial Analysis Intelligence Index task, segmented by token type. Lower is better

Cost to Run Artificial Analysis Intelligence Index

Cost (USD) to run all evaluations in the Artificial Analysis Intelligence Index

The cost to run the evaluations in the Artificial Analysis Intelligence Index, calculated using the model's input, cache hit, cache write, reasoning, and answer token prices and the number of tokens used across evaluations (excluding repeats).

Pricing: Cache Hit, Input, and Output

Price (USD per M Tokens)

Price per token for cached prompts (previously processed), typically offering a significant discount compared to regular input price, represented as USD per million tokens. The values shown here are the cache hit price; cache write and cache storage are billed separately and vary by provider — see "Cache pricing by provider" for detail.

Context Window

Context window: tokens limit · Higher is better

No publicly available API

Larger context windows are relevant to RAG (Retrieval Augmented Generation) LLM workflows which typically involve reasoning and information retrieval of large amounts of data.

Maximum number of combined input & output tokens. Output tokens commonly have a significantly lower limit (varied by model).

Frequently Asked Questions

Common questions about Grok 4 Fast (Reasoning)

Grok 4 Fast (Reasoning) was released on September 19, 2025.

Grok 4 Fast (Reasoning) was created by SpaceXAI.

Grok 4 Fast (Reasoning) scores 18 (estimated) on the Artificial Analysis Intelligence Index, placing it above average among other models in a similar price tier (median: 13).

Grok 4 Fast (Reasoning) costs $0.20 per 1M input tokens (better than average, median: $0.25) and $0.50 per 1M output tokens (very competitive, median: $0.87), based on the median across providers serving the model.

Grok 4 Fast (Reasoning) costs $0.20 per 1M input tokens and $0.50 per 1M output tokens (based on the median across providers serving the model). For a blended rate (7:2:1 cache hit/input/output ratio), this is $0.23 per 1M tokens. Pricing may vary by provider. Compare provider pricing

Yes, Grok 4 Fast (Reasoning) is a reasoning model. It uses extended thinking or chain-of-thought reasoning to work through complex problems before providing an answer.

Grok 4 Fast (Reasoning) supports text and image input.

Grok 4 Fast (Reasoning) supports text output.

Yes, Grok 4 Fast (Reasoning) supports image input and can analyze, describe, and answer questions about images.

Yes, Grok 4 Fast (Reasoning) is multimodal. It can process text and image input and generate text output.

Grok 4 Fast (Reasoning) has a context window of 2.0M tokens. This determines how much text and conversation history the model can process in a single request.

No, Grok 4 Fast (Reasoning) is proprietary. The model weights are not publicly available.

Grok 4 Fast (Reasoning) is a proprietary model and SpaceXAI has not disclosed the model size or parameter count.

Grok 4 Fast (Reasoning) achieves a score of 18 on the Artificial Analysis Intelligence Index. This composite benchmark evaluates models across reasoning, knowledge, mathematics, and coding.

Yes, Grok 4 Fast (Reasoning) is available via API through 1 provider. Compare API providers

Grok 4 Fast (Reasoning) is available through 1 API provider. Compare providers

Grok 4 Fast (Reasoning) Intelligence, Performance & Price Analysis

Model summary

Intelligence

Speed

Cost

Verbosity

Comparison Summary

Technical specifications

176 models in this class

Intelligence

Speed

Cost per Task

Intelligence

Artificial Analysis Intelligence Index

Artificial Analysis Intelligence Index

Artificial Analysis Intelligence Index by Open Weights / Proprietary

Artificial Analysis Intelligence Index

Open Weights

Intelligence Index vs. Cost per Intelligence Index Task

Cost per Intelligence Index Task

Artificial Analysis Intelligence Index

Benchmarks

Intelligence Evaluations

Intelligence Evaluation Relevance

Artificial Analysis Intelligence Index

AA-Omniscience

AA-Omniscience Index

AA-Omniscience Index

Intelligence Index Comparisons

Intelligence Index vs. Cost per Intelligence Index Task

Cost per Intelligence Index Task

Artificial Analysis Intelligence Index

Cost

Cost per Intelligence Index Task

Cost per Intelligence Index Task

Cost to Run Artificial Analysis Intelligence Index

Cost to Run Artificial Analysis Intelligence Index

Pricing: Cache Hit, Input, and Output

Cache Hit

Context Window

Context Window

Context Window for RAG

Context Window

Frequently Asked Questions

When was Grok 4 Fast (Reasoning) released?

Who created Grok 4 Fast (Reasoning)?

How intelligent is Grok 4 Fast (Reasoning)?

How much does Grok 4 Fast (Reasoning) cost?

What is Grok 4 Fast (Reasoning) API pricing?

Is Grok 4 Fast (Reasoning) a reasoning model?

What input modalities does Grok 4 Fast (Reasoning) support?

What output modalities does Grok 4 Fast (Reasoning) support?

Can Grok 4 Fast (Reasoning) process images?

Is Grok 4 Fast (Reasoning) multimodal?

What is the context window of Grok 4 Fast (Reasoning)?

Is Grok 4 Fast (Reasoning) open source?

How many parameters does Grok 4 Fast (Reasoning) have?

How does Grok 4 Fast (Reasoning) perform on benchmarks?

Is Grok 4 Fast (Reasoning) available via API?

Where can I use Grok 4 Fast (Reasoning)?