xAI: Grok 4 Fast
Analysis Summary
Grok 4 Fast is a multimodal xAI model with vision, file input, tool use, and function calling. Its two-million-token context is a standout for processing large document collections, and the listed input and output prices are low. Its measured intelligence index is limited, however, so the long context should not be mistaken for consistently strong reasoning.
It can suit high-volume document triage, first-pass summaries, and workflows where tools or image input are useful and a human can verify important outputs. The available data does not show strong coding or agentic results, so it is a weaker fit for autonomous engineering or sensitive decisions. Use it for routine work rather than final approval of client-facing claims.
The price and context make it practical to trial as a volume model. Keep quality checks in the workflow, particularly when outputs will be published or trigger downstream actions.
Assessed September 23, 2026
Editorial notes
Grok 4 Fast offers vision, file input, tool and function calling, and a two-million-token context at low listed prices; its measured intelligence is limited, so review is important for consequential work.
The DFO score ranks models on the Artificial Analysis Intelligence Index and is refreshed as new models launch. The write-up and verdict are our own. Feedback?
DFO Verdict
Grok 4 Fast offers vision, file input, tool and function calling, and a two-million-token context at low listed prices; its measured intelligence is limited, so review is important for consequential work.
Benchmarks
Artificial Analysis data refreshed Sep 30, 2026. Arena ratings from the Sep 25, 2026 text leaderboard, with style control.
Artificial Analysis has not published coding or agentic results for xAI: Grok 4 Fast yet. Until it does, the model sits below tested models on the Coding and AI Agents lists.
How xAI: Grok 4 Fast compares
XAI: Grok 4 Fast ranks #136 of 431 AI models we track for overall intelligence. Its 2M-token context window is larger than 100% of the models we list. At $0.20 per million input tokens it is cheaper than 52% of comparable models.
Dark bar = input · light bar = output, scaled to the priciest peer.
1M tokens ≈ 8 full-length novels or ~2,500 pages of business documents in a single request.
Pricing
| Token Type | Cost per 1M tokens | Cost per 1K tokens |
|---|---|---|
| Input | $0.20 | $0.000200 |
| Output | $0.50 | $0.000500 |
What would xAI: Grok 4 Fast cost your business?
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A website chatbot handling around 100 customer conversations a day, a few short messages each.
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These numbers get smaller with the right architecture.
We route routine calls to cheap models and save xAI: Grok 4 Fast for the hard ones. Most clients cut their estimate by 60-80%.
Talk to our teamAbout xAI: Grok 4 Fast
Grok 4 Fast is xAI's latest multimodal model with SOTA cost-efficiency and a 2M token context window. It comes in two flavors: non-reasoning and reasoning. Read more about the model..
Frequently asked questions about xAI: Grok 4 Fast
How much does xAI: Grok 4 Fast cost?
xAI: Grok 4 Fast costs $0.20 per million input tokens and $0.50 per million output tokens.
What is the context window of xAI: Grok 4 Fast?
xAI: Grok 4 Fast has a context window of 2,000,000 tokens (2M).
What can xAI: Grok 4 Fast do?
xAI: Grok 4 Fast supports image/vision input, tool use, and function calling.
Who created xAI: Grok 4 Fast?
xAI: Grok 4 Fast is developed by xAI and was released on September 19, 2025.