Grok-4 vs Grok 4 Fast
Grok-4 and Grok 4 Fast are closely matched at 33.9 and 32.0 on the LLM Stats Score. Grok 4 Fast is 21.8x cheaper per token.
xAI · xAI · Updated for 2026
Which is better?
Grok-4 and Grok 4 Fast are closely matched on the overall LLM Stats Score at 33.9 and 32.0.
The models split the 4 individual benchmarks reported for both models evenly.
On price, Grok 4 Fast is roughly 21.8x cheaper per token on a blended 3:1 input/output basis, which adds up quickly at production volume.
Grok 4 Fast also accepts a larger context window (2,000,000 input tokens), making it the stronger choice for long documents and large codebases.
Based on current LLM Stats indexes, shared benchmarks, pricing, and model metadata for 2026.
Choose Grok-4
- you want predictable pricing at $3.00/M input and $15.00/M output
Choose Grok 4 Fast
- cost matters — it's about 21.8x cheaper per token
- you process long inputs — it offers a 2,000,000 token context window
- you want the most recent training data — it shipped Aug 2025
At a glance
The differences that matter most.
Capability indexes
Additional strengths measured across groups of related public benchmarks
Individual benchmarks
7 reported for Grok-4 · 7 for Grok 4 Fast
Grok-4 outperforms in 2 benchmarks (GPQA, Humanity's Last Exam), while Grok 4 Fast is better at 2 benchmarks (AIME 2025, LiveCodeBench).
Both models are evenly matched across the benchmarks.
Human preference
Blind head-to-head votes and playground preference scores
Pricing Analysis
Price comparison per million tokens
For input processing, Grok-4 ($3.00/1M tokens) is 15.0x more expensive than Grok 4 Fast ($0.20/1M tokens).
For output processing, Grok-4 ($15.00/1M tokens) is 30.0x more expensive than Grok 4 Fast ($0.50/1M tokens).
In conclusion, Grok-4 is more expensive than Grok 4 Fast.*
* Using a 3:1 ratio of input to output tokens
Context Window
Maximum input and output token capacity
Grok 4 Fast accepts 2,000,000 input tokens compared to Grok-4's 256,000 tokens. Grok 4 Fast can generate longer responses up to 30,000 tokens, while Grok-4 is limited to 8,000 tokens.
Input capabilities
Documented input modalities across available providers
Both Grok-4 and Grok 4 Fast support multimodal inputs.
They are both capable of processing various types of data, offering versatility in application.
Grok-4
Grok 4 Fast
License
Usage and distribution terms
Both models are licensed under proprietary licenses.
Both models have usage restrictions defined by their respective organizations.
Proprietary
Closed source
Proprietary
Closed source
Release Timeline
When each model was launched
Grok-4 was released on 2025-07-09, while Grok 4 Fast was released on 2025-08-28.
Grok 4 Fast is 2 months newer than Grok-4.
Jul 9, 2025
1.2 years ago
Aug 28, 2025
1.0 years ago
1mo newerKnowledge Cutoff
When training data ends
Grok-4 has a documented knowledge cutoff of 2024-12-31, while Grok 4 Fast's cutoff date is not specified.
We can confirm Grok-4's training data extends to 2024-12-31, but cannot make a direct comparison without Grok 4 Fast's cutoff date.
Dec 2024
—
Provider Availability
Grok-4 is available from xAI. Grok 4 Fast is available from xAI.
Grok-4
Grok 4 Fast
Outputs Comparison
Judge for yourself.
Run your own prompts against Grok-4 and Grok 4 Fast side-by-side, then vote on the output you prefer.
FAQ
Common questions about Grok-4 vs Grok 4 Fast.