Z.ai: GLM 5.1 vs GPT-5 Pro
Compare Z.ai: GLM 5.1 by Z-ai against GPT-5 Pro by OpenAI, context windows of 203K vs 400K, tested across 40 shared challenges.
Our Verdict
GPT-5 Pro
Z.ai: GLM 5.1Runner-up
No community votes yet. On paper, GPT-5 Pro has the edge — bigger model tier, bigger context window, major provider backing.
Z.ai: GLM 5.1 is 27x cheaper per token — worth considering if cost matters.
Too close to call
API pricing
Cost per 1M tokens
Z.ai: GLM 5.1
Input
$1.40
11× cheaper
Output
$4.40
27× cheaper
GPT-5 Pro
Input
$15.00
Output
$120.00
Z.ai: GLM 5.1 is cheaper on both — 11× input, 27× output
Writing DNA
Style Comparison
Similarity
51%
Z.ai: GLM 5.1 uses 364.7x more bold
Z.ai: GLM 5.1
GPT-5 Pro
54%Vocabulary65%
18wSentence Length15w
0.31Hedging0.32
3.6Bold0.0
2.6Lists2.9
0.00Emoji0.00
0.43Headings0.00
0.11Transitions0.01
Based on 27 + 11 text responses
Research
What we learned reading every model
FAQ
Common questions
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