ChatGPT-4o (March 2025) vs Z.ai: GLM 5.1
Compare ChatGPT-4o (March 2025) by OpenAI against Z.ai: GLM 5.1 by Z-ai, context windows of 128K vs 203K, tested across 31 shared challenges. Updated April 2026.
Which is better, ChatGPT-4o (March 2025) or Z.ai: GLM 5.1?
ChatGPT-4o (March 2025) and Z.ai: GLM 5.1 are both competitive models. ChatGPT-4o (March 2025) costs $5/M input tokens vs $1.4/M for Z.ai: GLM 5.1. Context windows: 128K vs 203K tokens. Compare their real outputs side by side below.
Key Differences Between ChatGPT-4o (March 2025) and Z.ai: GLM 5.1
ChatGPT-4o (March 2025) is made by openai while Z.ai: GLM 5.1 is from z-ai. ChatGPT-4o (March 2025) has a 128K token context window compared to Z.ai: GLM 5.1's 203K. On pricing, ChatGPT-4o (March 2025) costs $5/M input tokens vs $1.4/M for Z.ai: GLM 5.1.
No community votes yet. On paper, these are closely matched - try both with your actual task to see which fits your workflow.
Z.ai: GLM 5.1 is 3.4x cheaper per token — worth considering if cost matters.
Style Comparison
ChatGPT-4o (March 2025) uses 94.5x more emoji
vsAsk them anything yourself
Some models write identically. You are paying for the brand.
178 models fingerprinted across 32 writing dimensions. Free research.
185x
price gap between models that write identically
178
models
12
clone pairs
32
dimensions
279 AI models invented the same fake scientist.
We read every word. 250 models. 2.14 million words. This is what we found.
