Claude Haiku 4.5 vs GPT-5 Nano

Compare Claude Haiku 4.5 by Anthropic against GPT-5 Nano by OpenAI, in 1 community votes, claude haiku 4.5 wins 100% of head-to-head duels, tested across 46 shared challenges. Updated April 2026.

Which is better, Claude Haiku 4.5 or GPT-5 Nano?

Claude Haiku 4.5 is the better choice overall, winning 100% of 1 blind community votes on Rival. Compare their real outputs side by side below.

Key Differences Between Claude Haiku 4.5 and GPT-5 Nano

Claude Haiku 4.5 is made by anthropic while GPT-5 Nano is from openai. In community voting, In 1 community votes, Claude Haiku 4.5 wins 100% of head-to-head duels.

In 1 community votes, Claude Haiku 4.5 wins 100% of head-to-head duels. Based on blind community voting from the Rival open dataset of 1+ human preference judgments for this pair.

Our Verdict
Claude Haiku 4.5
Claude Haiku 4.5Winner
GPT-5 Nano
GPT-5 NanoRunner-up

Pick Claude Haiku 4.5. In 1 blind votes, Claude Haiku 4.5 wins 100% of the time. That's not luck.

Clear winner
Writing DNA

Style Comparison

Similarity
100%

Claude Haiku 4.5 uses 513.9x more bold

Claude Haiku 4.5
GPT-5 Nano
61%Vocabulary59%
47wSentence Length25w
0.64Hedging0.23
5.1Bold0.0
6.3Lists4.2
0.20Emoji0.00
2.46Headings0.00
0.17Transitions0.01
Based on 24 + 14 text responses
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Claude Haiku 4.5GPT-5 Nano

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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