GPT-5.1-Codex vs Grok 3

Compare GPT-5.1-Codex by OpenAI against Grok 3 by xAI, context windows of 400K vs 128K, tested across 52 shared challenges. Updated April 2026.

Which is better, GPT-5.1-Codex or Grok 3?

GPT-5.1-Codex and Grok 3 are both competitive models. Context windows: 400K vs 128K tokens. Compare their real outputs side by side below.

Key Differences Between GPT-5.1-Codex and Grok 3

GPT-5.1-Codex is made by openai while Grok 3 is from xai. GPT-5.1-Codex has a 400K token context window compared to Grok 3's 128K.

Our Verdict
GPT-5.1-Codex
GPT-5.1-Codex
Grok 3
Grok 3Runner-up

No community votes yet. On paper, GPT-5.1-Codex has the edge — newer, bigger context window.

Too close to call
Writing DNA

Style Comparison

Similarity
95%

Grok 3 uses 3.9x more emoji

GPT-5.1-Codex
Grok 3
70%Vocabulary49%
17wSentence Length18w
0.39Hedging0.94
3.4Bold2.5
3.5Lists3.0
0.00Emoji0.04
0.50Headings0.65
0.38Transitions0.08
Based on 14 + 17 text responses
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GPT-5.1-CodexGrok 3

279 AI models invented the same fake scientist.

We read every word. 250 models. 2.14 million words. This is what we found.

AI Hallucination Index 2026
Free preview13 of 58 slides
FAQ

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