xAI: Grok 4 Fast

Public pricingIntelligence 79/100Huge memoryVisionDeep thinkingTool use

xAI: Grok 4 Fast is a multimodal model for multimodal reasoning and analysis. It combines multimodal input handling and deep reasoning and planning with a 1M+ tokens context window and a low-cost profile. Use it for multimodal reasoning and analysis when latency, cost, and throughput matters.

Input

$0.20/1M

Output

$0.50/1M

Cached

$0.05/1M

Batch

$0.10/1M

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What would Grok 4 Fast cost you?

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1,00010,00050,000250,0001M10M

Technical specifications

Grok 4 Fast at a glance.

Memory

2,000,000

tokens

Max reply

30,000

tokens

Memory tier

Huge

multiple books or whole repositories

Tokenizer

grok

Released

Sep 2025

Training cutoff

Mar 2025

Availability

Public pricing

Status

active

What it can do

Capabilities & limits.

  • Understands images
  • Deep step-by-step thinking
  • Uses tools / calls functions
  • Strict JSON output
  • Streams replies
  • Fine-tunable on your data

When to pick Grok 4 Fast

  • Multi-step reasoning, research agents, or hard math.
  • Screenshot analysis, image understanding, or document OCR.
  • Agentic workflows that call tools or APIs.
  • Long documents, full codebases, or extensive chat histories.

When to look elsewhere

  • Very latency-sensitive, real-time apps where every millisecond counts.

Alternatives

Similar models to compare.

FAQ

Grok 4 Fast — the questions we see most.

Pricing, capabilities, alternatives — generated from the same data that powers the calculator above.

Get instant answers from our AI agent

At a typical workload of 50,000 conversations a month with 1,500-token prompts and 800-token replies, Grok 4 Fast costs roughly $35 per month. Input is $0.20 /1M tokens and output is $0.50 /1M tokens.
Grok 4 Fast has a 2,000,000-token context window (huge memory — multiple books or whole repositories). That means you can fit about 375,000 words of input and history in a single call.
Beyond text generation, Grok 4 Fast supports understanding images, deep step-by-step reasoning, calling functions / tools, strict JSON output. It streams replies by default.
Grok 4 Fast was released in September 2025, with training data cut off around March 2025.
Models in a similar class include Grok 4.1 Fast, GPT-5.4 Nano, Gemini 3.1 Flash Lite Preview. The "Similar models" section below this FAQ links into each.

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