GLM-5.1 vs GPT-5.5
GLM-5.1 (2026) and GPT-5.5 (2026) are frontier-tier reasoning models from Zhipu AI and OpenAI. GLM-5.1 ships a 200k-token context window, while GPT-5.5 ships a 1M-token context window. On Google-Proof Q&A, GPT-5.5 leads by 6.8 pts. On pricing, GLM-5.1 costs $0.95/1M input tokens versus $5/1M for the alternative. This comparison covers specs, pricing, capabilities, benchmarks, provider availability, and production fit. It focuses on practical selection signals rather than broad model-family marketing.
GLM-5.1 is ~426% cheaper at $0.95/1M; pay for GPT-5.5 only for coding workflow support.
Specs
Pricing and availability
| GLM-5.1 | GPT-5.5 | |
|---|---|---|
| Input price | $0.95/1M tokens | $5/1M tokens |
| Output price | $3.15/1M tokens | $30/1M tokens |
| Providers |
Capabilities
| GLM-5.1 | GPT-5.5 | |
|---|---|---|
| Vision | ||
| Multimodal | ||
| Reasoning | ||
| Function calling | ||
| Tool use | ||
| Structured outputs | ||
| Code execution |
Benchmarks
| Benchmark | GLM-5.1 | GPT-5.5 |
|---|---|---|
| Google-Proof Q&A | 86.8 | 93.6 |
| SWE-bench Pro | 58.4 | 58.6 |
Deep dive
On shared benchmark coverage, Google-Proof Q&A has GLM-5.1 at 86.8 and GPT-5.5 at 93.6, with GPT-5.5 ahead by 6.8 points; SWE-bench Pro has GLM-5.1 at 58.4 and GPT-5.5 at 58.6, with GPT-5.5 ahead by 0.2 points. The largest visible gap is 6.8 points on Google-Proof Q&A, which matters most when that benchmark mirrors your workload. Treat isolated benchmark wins as directional, because provider routing, prompt style, and tool access can move real application results.
The capability footprint differs most on vision: GPT-5.5 and multimodal input: GPT-5.5. Both models share reasoning mode, function calling, tool use, and structured outputs, so the practical split is not just feature count. Use those differences to decide whether the page is about raw model quality, agentic coding support, multimodal ingestion, or predictable structured API behavior.
For cost, GLM-5.1 lists $0.95/1M input and $3.15/1M output tokens, while GPT-5.5 lists $5/1M input and $30/1M output tokens on the cheapest tracked provider. A 70/30 input-output blend puts GLM-5.1 lower by about $10.89 per million blended tokens. Availability is 2 providers versus 1, so concentration risk also matters.
Choose GLM-5.1 when coding workflow support, lower input-token cost, and broader provider choice are central to the workload. Choose GPT-5.5 when coding workflow support and larger context windows are more important. For production, rerun your own prompts through the exact provider, region, and tool stack you plan to ship.
FAQ
Which has a larger context window, GLM-5.1 or GPT-5.5?
GPT-5.5 supports 1M tokens, while GLM-5.1 supports 200k tokens. That gap matters most for long documents, large codebases, retrieval-heavy agents, and conversations where earlier context must remain visible. Use this as a quick comparison signal, then confirm the provider-specific limits before committing to production.
Which is cheaper, GLM-5.1 or GPT-5.5?
GLM-5.1 is cheaper on tracked token pricing. GLM-5.1 costs $0.95/1M input and $3.15/1M output tokens. GPT-5.5 costs $5/1M input and $30/1M output tokens. Provider discounts or batch pricing can still change the final bill.
Is GLM-5.1 or GPT-5.5 open source?
GLM-5.1 is listed under Proprietary. GPT-5.5 is listed under Proprietary. License labels affect whether you can self-host, redistribute weights, or rely only on hosted APIs, so confirm the upstream license before deployment.
Which is better for vision, GLM-5.1 or GPT-5.5?
GPT-5.5 has the clearer documented vision signal in this comparison. If vision is mission-critical, validate it against the provider endpoint because model-level support and API-level exposure can differ. Use this as a quick comparison signal, then confirm the provider-specific limits before committing to production.
Which is better for multimodal input, GLM-5.1 or GPT-5.5?
GPT-5.5 has the clearer documented multimodal input signal in this comparison. If multimodal input is mission-critical, validate it against the provider endpoint because model-level support and API-level exposure can differ.
Where can I run GLM-5.1 and GPT-5.5?
GLM-5.1 is available on Z.ai and OpenRouter. GPT-5.5 is available on OpenAI API. Provider coverage can affect latency, region availability, compliance posture, and fallback options. Use this as a quick comparison signal, then confirm the provider-specific limits before committing to production.
Continue comparing
Last reviewed: 2026-04-24. Data sourced from public model cards and provider documentation.