GLM-5.1 vs GPT-5.5
GPT-5.5 significantly outperforms across most benchmarks. GLM-5.1 is 5.2x cheaper per token.
Zhipu AI · OpenAI · Updated for 2026
Which is better?
GLM-5.1 outperforms in 1 benchmarks (Humanity's Last Exam), while GPT-5.5 is better at 10 benchmarks (BrowseComp, CyberGym, Finance Agent v2, FrontierSWE, GPQA, LiveBench, MCP Atlas, SWE-Bench Pro, Terminal-Bench 2.0, Toolathlon). GPT-5.5 significantly outperforms across most benchmarks.
On price, GLM-5.1 is roughly 5.2x cheaper per token on a blended 3:1 input/output basis, which adds up quickly at production volume.
GPT-5.5 also accepts a larger context window (1,050,000 input tokens), making it the stronger choice for long documents and large codebases.
Based on current benchmark, pricing, and model metadata for 2026.
Choose GLM-5.1
- cost matters — it's about 5.2x cheaper per token
- you need open weights you can self-host or fine-tune
Choose GPT-5.5
- you want the strongest raw capability — it leads on 10 of 11 shared benchmarks
- you process long inputs — it offers a 1,050,000 token context window
- you want the most recent training data — it shipped Apr 2026
At a glance
The differences that matter most.
Performance Benchmarks
Comparative analysis across standard metrics
GLM-5.1 outperforms in 1 benchmarks (Humanity's Last Exam), while GPT-5.5 is better at 10 benchmarks (BrowseComp, CyberGym, Finance Agent v2, FrontierSWE, GPQA, LiveBench, MCP Atlas, SWE-Bench Pro, Terminal-Bench 2.0, Toolathlon).
GPT-5.5 significantly outperforms across most benchmarks.
Arena Performance
Playground indexes and blind preference scores
Pricing Analysis
Price comparison per million tokens
For input processing, GLM-5.1 ($1.40/1M tokens) is 3.6x cheaper than GPT-5.5 ($5.00/1M tokens).
For output processing, GLM-5.1 ($4.40/1M tokens) is 6.8x cheaper than GPT-5.5 ($30.00/1M tokens).
In conclusion, GPT-5.5 is more expensive than GLM-5.1.*
* Using a 3:1 ratio of input to output tokens
Context Window
Maximum input and output token capacity
GPT-5.5 accepts 1,050,000 input tokens compared to GLM-5.1's 200,000 tokens. Both models can generate responses up to 128,000 tokens.
Input Capabilities
Supported data types and modalities
GPT-5.5 supports multimodal inputs, whereas GLM-5.1 does not.
GPT-5.5 can handle both text and other forms of data like images, making it suitable for multimodal applications.
GLM-5.1
GPT-5.5
License
Usage and distribution terms
GLM-5.1 is licensed under MIT, while GPT-5.5 uses a proprietary license.
License differences may affect how you can use these models in commercial or open-source projects.
MIT
Open weights
Proprietary
Closed source
Release Timeline
When each model was launched
GLM-5.1 was released on 2026-04-07, while GPT-5.5 was released on 2026-04-23.
GPT-5.5 is 1 month newer than GLM-5.1.
Apr 7, 2026
4 months ago
Apr 23, 2026
4 months ago
2w newerKnowledge Cutoff
When training data ends
GPT-5.5 has a documented knowledge cutoff of 2025-12-01, while GLM-5.1's cutoff date is not specified.
We can confirm GPT-5.5's training data extends to 2025-12-01, but cannot make a direct comparison without GLM-5.1's cutoff date.
—
Dec 2025
Provider Availability
GLM-5.1 is available from FriendliAI, ZAI. GPT-5.5 is available from OpenAI.
GLM-5.1
GPT-5.5
Outputs Comparison
Judge for yourself.
Run your own prompts against GLM-5.1 and GPT-5.5 side-by-side, then vote on the output you prefer.
FAQ
Common questions about GLM-5.1 vs GPT-5.5.