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Claude Opus 4.5 vs GPT-4o mini

Compare Claude Opus 4.5 by Anthropic against GPT-4o mini by OpenAI, tested across 38 shared challenges. Updated April 2026.

Which is better, Claude Opus 4.5 or GPT-4o mini?

Claude Opus 4.5 and GPT-4o mini are both competitive models. Compare their real outputs side by side below.

Key Differences Between Claude Opus 4.5 and GPT-4o mini

Claude Opus 4.5 is made by anthropic while GPT-4o mini is from openai.

Our Verdict
Claude Opus 4.5
Claude Opus 4.5
GPT-4o mini
GPT-4o miniRunner-up

No community votes yet. On paper, Claude Opus 4.5 has the edge — bigger model tier, newer.

Too close to call
Writing DNA

Style Comparison

Similarity
94%

Claude Opus 4.5 uses 15.2x more emoji

Claude Opus 4.5
GPT-4o mini
64%Vocabulary54%
55wSentence Length18w
0.86Hedging0.84
5.8Bold3.8
4.5Lists3.3
0.15Emoji0.00
1.59Headings1.03
0.05Transitions0.23
Based on 24 + 22 text responses
vs

Ask them anything yourself

Claude Opus 4.5GPT-4o 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
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