GLM-5.3-Flash vs GPT-5.5
GLM-5.3-Flash shows notably better performance in the majority of benchmarks. GLM-5.3-Flash is 47.4x cheaper per token.
Zhipu AI · OpenAI · Updated for 2026
Which is better?
GLM-5.3-Flash outperforms in 3 benchmarks (Humanity's Last Exam, OfficeQA Pro, Toolathlon), while GPT-5.5 is better at 1 benchmark (DeepSWE 1.1). GLM-5.3-Flash shows notably better performance in the majority of benchmarks.
On price, GLM-5.3-Flash is roughly 47.4x 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-5.3-Flash
- you want the strongest raw capability — it leads on 3 of 4 shared benchmarks
- cost matters — it's about 47.4x cheaper per token
- you want the most recent training data — it shipped Aug 2026
- you need open weights you can self-host or fine-tune
Choose GPT-5.5
- you process long inputs — it offers a 1,050,000 token context window
At a glance
The differences that matter most.
Performance Benchmarks
Comparative analysis across standard metrics
GLM-5.3-Flash outperforms in 3 benchmarks (Humanity's Last Exam, OfficeQA Pro, Toolathlon), while GPT-5.5 is better at 1 benchmark (DeepSWE 1.1).
GLM-5.3-Flash shows notably better performance in the majority of benchmarks.
Arena Performance
Playground indexes and blind preference scores
Pricing Analysis
Price comparison per million tokens
For input processing, GLM-5.3-Flash ($0.15/1M tokens) is 33.3x cheaper than GPT-5.5 ($5.00/1M tokens).
For output processing, GLM-5.3-Flash ($0.50/1M tokens) is 60.0x cheaper than GPT-5.5 ($30.00/1M tokens).
In conclusion, GPT-5.5 is more expensive than GLM-5.3-Flash.*
* 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-5.3-Flash's 1,048,576 tokens. GLM-5.3-Flash can generate longer responses up to 131,072 tokens, while GPT-5.5 is limited to 128,000 tokens.
Input Capabilities
Supported data types and modalities
Both GLM-5.3-Flash and GPT-5.5 support multimodal inputs.
They are both capable of processing various types of data, offering versatility in application.
GLM-5.3-Flash
GPT-5.5
License
Usage and distribution terms
GLM-5.3-Flash 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-5.3-Flash was released on 2026-08-26, while GPT-5.5 was released on 2026-04-23.
GLM-5.3-Flash is 4 months newer than GPT-5.5.
Aug 26, 2026
1 days ago
4mo newerApr 23, 2026
4 months ago
Knowledge Cutoff
When training data ends
GPT-5.5 has a documented knowledge cutoff of 2025-12-01, while GLM-5.3-Flash'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-5.3-Flash's cutoff date.
—
Dec 2025
Provider Availability
GLM-5.3-Flash is available from DeepInfra, Novita, ZAI. GPT-5.5 is available from OpenAI.
GLM-5.3-Flash
GPT-5.5
Outputs Comparison
Judge for yourself.
Run your own prompts against GLM-5.3-Flash and GPT-5.5 side-by-side, then vote on the output you prefer.
FAQ
Common questions about GLM-5.3-Flash vs GPT-5.5.