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Comparison · 2 models · Updated Nov 2, 2026

Grok 4 Fast Reasoning vs Grok 4.1 Fast

Grok 4 Fast Reasoning comes out ahead, 75 to 66 on our weighted score.

  1. Our pick

    xAI

    Grok 4 Fast Reasoning

    Released Dec 18, 2025

    75/100
    • ECI—
    • Price$0.20 / $0.50
    • Context2M
    Full specs Remove Grok 4 Fast Reasoning

  2. xAI

    Grok 4.1 Fast

    Released Nov 19, 2025

    66/100
    • ECI—
    • Price$0.20 / $0.50
    • Context2M
    Full specs Remove Grok 4.1 Fast

  3. Add a model

    Make it a three-way comparison.

01 — Verdict

Grok 4 Fast Reasoning is our pick

Grok 4 Fast Reasoning is the better all-round choice, scoring 75/100 against Grok 4.1 Fast (66). It leads on inputs & features. The score weighs price 50%, inputs & features 30%, context window 20%. None of the shared benchmarks cover every model here yet, so capability is left out of this verdict.

  • CapabilityNot enough dataNo independent benchmark covers every model here yet
  • Lowest priceSame priceGrok 4 Fast Reasoning $0.275 · Grok 4.1 Fast $0.275 per 1M tokens (3:1 blend)
  • Longest contextAbout the sameGrok 4 Fast Reasoning 2,000,000 · Grok 4.1 Fast 2,000,000 tokens
  • Widest inputsGrok 4 Fast ReasoningGrok 4 Fast Reasoning: Text, Images, Audio, Video · Grok 4.1 Fast: Text, Images
  • Self-hostingNo open weightsBoth are available only through APIs
How the score is built
MeasureWeightGrok 4 Fast ReasoningGrok 4.1 Fast
Price50%7373
Inputs & features30%8050
Context window20%7272
Overall100%75/10066/100

Left out because at least one model lacks the data: capability. The remaining weights were rescaled.

02 — Side by side

Every spec in one table

Highlighted cells lead their row. Dashes mean the data is not published.

Grok 4 Fast Reasoning vs Grok 4.1 Fast specifications side by side
SpecificationGrok 4 Fast ReasoningxAIGrok 4.1 FastxAI
Capability
Capabilities Index (ECI)——
ECI rank——
Price per million tokens
Input$0.20$0.20
Output$0.50$0.50
Cached input——
Blended (3:1)$0.275$0.275
Long-context rateSame rateSame rate
Price sourceMedian of 4 providersMedian of 6 providers
Limits
Context window2,000,000 tokens2,000,000 tokens
Max output2,000,000 tokens (best)30,000 tokens
Inputs and features
TextYesYes
ImagesYesYes
PDFsNoNo
AudioYesNo
VideoYesNo
ReasoningYesNo
Tool callingYesYes
Structured outputNoNo
Availability
WeightsProprietaryProprietary
API model ID——
API providers58 (best)
ReleasedDec 18, 2025Nov 19, 2025
Knowledge cutoff——
03 — Cost

What would a month cost?

Enter your expected volume in millions of tokens. List prices only; caching and batch discounts would lower these.

  • Grok 4 Fast Reasoning$3.00
  • Grok 4.1 Fast$3.00
04 — Questions

Which should you choose?

Which is better: Grok 4 Fast Reasoning or Grok 4.1 Fast?

Grok 4 Fast Reasoning is the better all-round choice, scoring 75/100 against Grok 4.1 Fast (66). It leads on inputs & features. The score weighs price 50%, inputs & features 30%, context window 20%. None of the shared benchmarks cover every model here yet, so capability is left out of this verdict.

Which is cheaper, Grok 4 Fast Reasoning or Grok 4.1 Fast?

Grok 4 Fast Reasoning and Grok 4.1 Fast cost the same: $0.20 input / $0.50 output per million tokens.

Which scores higher on benchmarks?

There is no independent benchmark that covers both models yet. Grok 4 Fast Reasoning has not been scored yet and Grok 4.1 Fast has not been scored yet.

Which is better for coding?

There are no published SWE-bench Verified results for Grok 4 Fast Reasoning and Grok 4.1 Fast yet, so there is no like-for-like coding score. Test both on a sample of your own tasks. Both support tool calling for agent workflows.

Which has the bigger context window?

Grok 4 Fast Reasoning and Grok 4.1 Fast share the same 2,000,000-token context window. Maximum output per response: Grok 4 Fast Reasoning up to 2,000,000, Grok 4.1 Fast up to 30,000 tokens.

Which can read images, PDFs, audio or video?

Grok 4 Fast Reasoning accepts text, images, audio and video; Grok 4.1 Fast accepts text and images. Grok 4 Fast Reasoning handles the widest range of inputs.

Are any of these open source?

No. Grok 4 Fast Reasoning and Grok 4.1 Fast are proprietary and only available through APIs and apps.

Which is newer?

Grok 4 Fast Reasoning is the newest, released Dec 18, 2025. Grok 4.1 Fast came out Nov 19, 2025.

How do you decide the winner?

Each model gets a 0–100 score on capability (50%, independent benchmark results); price (25%, blended price per million tokens (3 input : 1 output), log scale); inputs & features (15%, image, PDF, audio and video input, tool calling, structured output and reasoning); context window (10%, maximum tokens per request, log scale). Dimensions missing for any model are dropped and the remaining weights rescaled, so every model is judged on the same evidence. Specs and prices come from public model listings and the labs’ own API pages; capability scores come from independent benchmark runs. Data updated Nov 2, 2026.

05 — Keep comparing

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