Z.ai: GLM 5.1 vs GPT-5.1

Compare Z.ai: GLM 5.1 by Z-ai against GPT-5.1 by OpenAI, context windows of 203K vs 400K, tested across 50 shared challenges. Updated April 2026.

Which is better, Z.ai: GLM 5.1 or GPT-5.1?

Z.ai: GLM 5.1 and GPT-5.1 are both competitive models. Z.ai: GLM 5.1 costs $1.4/M input tokens vs $1.25/M for GPT-5.1. Context windows: 203K vs 400K tokens. Compare their real outputs side by side below.

Key Differences Between Z.ai: GLM 5.1 and GPT-5.1

Z.ai: GLM 5.1 is made by z-ai while GPT-5.1 is from openai. Z.ai: GLM 5.1 has a 203K token context window compared to GPT-5.1's 400K. On pricing, Z.ai: GLM 5.1 costs $1.4/M input tokens vs $1.25/M for GPT-5.1.

Our Verdict
GPT-5.1
GPT-5.1
Z.ai: GLM 5.1
Z.ai: GLM 5.1Runner-up

No community votes yet. On paper, GPT-5.1 has the edge — bigger model tier, bigger context window, major provider backing.

Too close to call
Writing DNA

Style Comparison

Similarity
99%

Z.ai: GLM 5.1 uses 3.9x more transitions

Z.ai: GLM 5.1
GPT-5.1
54%Vocabulary62%
18wSentence Length19w
0.31Hedging0.29
3.6Bold3.5
2.6Lists7.2
0.00Emoji0.00
0.43Headings0.61
0.11Transitions0.03
Based on 27 + 14 text responses
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Ask them anything yourself

Z.ai: GLM 5.1GPT-5.1

279 AI models invented the same fake scientist.

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

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