GPT-5 Pro vs xAI: Grok 4 Fast (free)
Compare GPT-5 Pro by OpenAI against xAI: Grok 4 Fast (free) by xAI, context windows of 400K vs 2.0M, tested across 24 shared challenges. Updated April 2026.
Which is better, GPT-5 Pro or xAI: Grok 4 Fast (free)?
GPT-5 Pro and xAI: Grok 4 Fast (free) are both competitive models. GPT-5 Pro costs $15/M input tokens vs $0/M for xAI: Grok 4 Fast (free). Context windows: 400K vs 2000K tokens. Compare their real outputs side by side below.
Key Differences Between GPT-5 Pro and xAI: Grok 4 Fast (free)
GPT-5 Pro is made by openai while xAI: Grok 4 Fast (free) is from xai. GPT-5 Pro has a 400K token context window compared to xAI: Grok 4 Fast (free)'s 2000K. On pricing, GPT-5 Pro costs $15/M input tokens vs $0/M for xAI: Grok 4 Fast (free).
No community votes yet. On paper, these are closely matched - try both with your actual task to see which fits your workflow.
Style Comparison
xAI: Grok 4 Fast (free) uses 138.0x more bold
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Some models write identically. You are paying for the brand.
178 models fingerprinted across 32 writing dimensions. Free research.
185x
price gap between models that write identically
178
models
12
clone pairs
32
dimensions
279 AI models invented the same fake scientist.
We read every word. 250 models. 2.14 million words. This is what we found.
