xAI

Grok 4 Fast

2M ctxTextImage Tools Reasoning

Released Sep 19, 2025 · 468B tokens this week · 2 providers

Overview

A cost-optimised Grok 4 with a two-million-token window and unusually low pricing for its class. Designed for search-heavy and high-volume agent workloads where you cannot afford flagship rates. The value leader in the xAI line by a wide margin.

agentsreasoningmarketing

Providers

Reference data — not yet measured from live traffic

PROVIDER		MAX OUT		OUTPUT /M				QUANT
xAICheapest	2M	30K	$0.20	$0.50	187ms	165	99.80%	Full
Azure AI Foundry	262K	30K	$0.22	$0.55	500ms	140	99.65%	Full

Latency p50 reflects a provider’s API endpoint responsiveness — the round-trip to its API, not per-token inference time. These figures, with throughput and uptime, are reference data until the gateway aggregates its own traffic.

Price comparison

Blended $ per 1M tokens

DeepSeek V3.2$0.37

Grok 4 Fast$0.42

Gemini 3 Flash$1.95

GPT-5.2$10.94

Claude Sonnet 4.5$12.00

Blended rate per 1M tokens, weighted one part prompt to three parts completion — roughly the shape of a chat workload. Your mix will move the number.

Call it

OpenAI-compatible — swap the base URL and go

curl https://model.cards/api/v1/chat/completions \
  -H "Authorization: Bearer $MODELCARDS_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "x-ai/grok-4-fast",
    "messages": [
      { "role": "user", "content": "Summarize the tradeoffs of speculative decoding." }
    ]
  }'