Claude Opus 4 vs Z.ai: GLM 5.1

Compare Claude Opus 4 by Anthropic against Z.ai: GLM 5.1 by Z-ai, context windows of 200K vs 203K, tested across 34 shared challenges. Updated April 2026.

Which is better, Claude Opus 4 or Z.ai: GLM 5.1?

Claude Opus 4 and Z.ai: GLM 5.1 are both competitive models. Claude Opus 4 costs $15/M input tokens vs $1.4/M for Z.ai: GLM 5.1. Context windows: 200K vs 203K tokens. Compare their real outputs side by side below.

Key Differences Between Claude Opus 4 and Z.ai: GLM 5.1

Claude Opus 4 is made by anthropic while Z.ai: GLM 5.1 is from z-ai. Claude Opus 4 has a 200K token context window compared to Z.ai: GLM 5.1's 203K. On pricing, Claude Opus 4 costs $15/M input tokens vs $1.4/M for Z.ai: GLM 5.1.

Our Verdict
Claude Opus 4
Claude Opus 4
Z.ai: GLM 5.1
Z.ai: GLM 5.1Runner-up

No community votes yet. On paper, Claude Opus 4 has the edge — bigger model tier, major provider backing.

Z.ai: GLM 5.1 is 17x cheaper per token — worth considering if cost matters.

Too close to call
Writing DNA

Style Comparison

Similarity
98%

Claude Opus 4 uses 11.2x more emoji

Claude Opus 4
Z.ai: GLM 5.1
64%Vocabulary54%
62wSentence Length18w
0.52Hedging0.31
4.4Bold3.6
9.1Lists2.6
0.11Emoji0.00
1.87Headings0.43
0.27Transitions0.11
Based on 16 + 27 text responses
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Claude Opus 4Z.ai: GLM 5.1

279 AI models invented the same fake scientist.

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