Claude 3 Opus vs Z.ai: GLM 5.1

Compare Claude 3 Opus by Anthropic against Z.ai: GLM 5.1 by Z-ai, context windows of 200K vs 203K, tested across 12 shared challenges. Updated April 2026.

Which is better, Claude 3 Opus or Z.ai: GLM 5.1?

Claude 3 Opus and Z.ai: GLM 5.1 are both competitive models. Claude 3 Opus 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 3 Opus and Z.ai: GLM 5.1

Claude 3 Opus is made by anthropic while Z.ai: GLM 5.1 is from z-ai. Claude 3 Opus has a 200K token context window compared to Z.ai: GLM 5.1's 203K. On pricing, Claude 3 Opus costs $15/M input tokens vs $1.4/M for Z.ai: GLM 5.1.

Our Verdict
Claude 3 Opus
Claude 3 Opus
Z.ai: GLM 5.1
Z.ai: GLM 5.1Runner-up

No community votes yet. On paper, Claude 3 Opus 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
92%

Z.ai: GLM 5.1 uses 364.7x more bold

Claude 3 Opus
Z.ai: GLM 5.1
54%Vocabulary54%
14wSentence Length18w
0.48Hedging0.31
0.0Bold3.6
3.0Lists2.6
0.00Emoji0.00
0.00Headings0.43
0.06Transitions0.11
Based on 3 + 27 text responses
vs

Ask them anything yourself

Claude 3 OpusZ.ai: GLM 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.

AI Hallucination Index 2026
Free preview13 of 58 slides
FAQ

Common questions