Claude 3 Sonnet vs OpenAI o3

Compare Claude 3 Sonnet by Anthropic against OpenAI o3 by OpenAI, tested across 13 shared challenges. Updated April 2026.

Which is better, Claude 3 Sonnet or OpenAI o3?

Claude 3 Sonnet and OpenAI o3 are both competitive models. Claude 3 Sonnet costs $3/M input tokens vs $10/M for OpenAI o3. Compare their real outputs side by side below.

Key Differences Between Claude 3 Sonnet and OpenAI o3

Claude 3 Sonnet is made by anthropic while OpenAI o3 is from openai. On pricing, Claude 3 Sonnet costs $3/M input tokens vs $10/M for OpenAI o3.

Our Verdict
OpenAI o3
OpenAI o3
Claude 3 Sonnet
Claude 3 SonnetRunner-up

No community votes yet. On paper, OpenAI o3 has the edge — bigger model tier, newer.

Too close to call
Writing DNA

Style Comparison

Similarity
99%

OpenAI o3 uses 69.5x more bold

Claude 3 Sonnet
OpenAI o3
48%Vocabulary68%
14wSentence Length14w
0.32Hedging0.26
0.0Bold0.7
3.6Lists3.0
0.00Emoji0.00
0.00Headings0.38
0.38Transitions0.12
Based on 4 + 16 text responses
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Claude 3 SonnetOpenAI o3

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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