Claude 3 Opus vs o3 Mini

Compare Claude 3 Opus by Anthropic against o3 Mini by OpenAI, context windows of 200K vs 64K, tested across 12 shared challenges. Updated April 2026.

Which is better, Claude 3 Opus or o3 Mini?

Claude 3 Opus and o3 Mini are both competitive models. Claude 3 Opus costs $15/M input tokens vs $1.1/M for o3 Mini. Context windows: 200K vs 64K tokens. Compare their real outputs side by side below.

Key Differences Between Claude 3 Opus and o3 Mini

Claude 3 Opus is made by anthropic while o3 Mini is from openai. Claude 3 Opus has a 200K token context window compared to o3 Mini's 64K. On pricing, Claude 3 Opus costs $15/M input tokens vs $1.1/M for o3 Mini.

Our Verdict
Claude 3 Opus
Claude 3 Opus
o3 Mini
o3 MiniRunner-up

No community votes yet. On paper, Claude 3 Opus has the edge — bigger model tier, bigger context window.

o3 Mini is 17x cheaper per token — worth considering if cost matters.

Too close to call
Writing DNA

Style Comparison

Similarity
100%

o3 Mini uses 390.2x more bold

Claude 3 Opus
o3 Mini
54%Vocabulary65%
14wSentence Length17w
0.48Hedging0.74
0.0Bold3.9
3.0Lists1.7
0.00Emoji0.00
0.00Headings0.47
0.06Transitions0.38
Based on 3 + 12 text responses
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Claude 3 Opuso3 Mini

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
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