Gemini 3.5 Flash vs GLM-5.1
Gemini 3.5 Flash and GLM-5.1 are both current production-tier models. GLM-5.1 is meaningfully cheaper at $1.4 / $4.4 per 1M. Gemini 3.5 Flash has a 1.0M context window — about 5× the 200k of GLM-5.1. Gemini 3.5 Flash leads on long-context retrieval, instruction following, tool use.
Specs side by side
| Metric | Google Gemini 3.5 Flash | Z.ai GLM-5.1 |
|---|---|---|
| Input price (per 1M) | $1.5 | $1.4 |
| Output price (per 1M) | $9 | $4.4 |
| Context window | 1.0M tokens | 200k tokens |
| Speed tier | fast | balanced |
| Open weights | No | Yes |
| EU region | Yes | No |
| Free tier | Google AI Studio | bigmodel.cn |
| Prompt caching | Yes | Yes |
| Vision input | Yes | No |
| Extended thinking | Yes | Yes |
When to choose each
Choose Gemini 3.5 Flash if…
- You need 1.0M context (5× more than GLM-5.1)
- EU data residency is required
- HIPAA eligibility is required
- You need image input / vision
- Long-context retrieval is central to your workload
- Instruction following is central to your workload
Choose GLM-5.1 if…
- Cost is a priority ($1.4 / $4.4 per 1M vs $1.5 / $9 per 1M)
- You need open weights for self-hosting or fine-tuning
Benchmark delta
Gemini 3.5 Flash leads on
- Long-context retrieval
- Instruction following
- Tool use
GLM-5.1 leads on
GLM-5.1 has no meaningful benchmark lead in this pair.
FAQ — Gemini 3.5 Flash vs GLM-5.1
Gemini 3.5 Flash vs GLM-5.1 — which is better?
Gemini 3.5 Flash and GLM-5.1 are both current production-tier models. GLM-5.1 is meaningfully cheaper at $1.4 / $4.4 per 1M. Gemini 3.5 Flash has a 1.0M context window — about 5× the 200k of GLM-5.1. Gemini 3.5 Flash leads on long-context retrieval, instruction following, tool use. The right pick depends on your use case — see "When to choose each" above for a data-driven decision.
How does Gemini 3.5 Flash pricing compare to GLM-5.1?
Gemini 3.5 Flash costs $1.5 / $9 per 1M vs GLM-5.1 at $1.4 / $4.4 per 1M. GLM-5.1 is cheaper on output tokens by roughly 105%. Both support prompt caching, which reduces effective cost by 80-90% on repeat system prompts.
Does Gemini 3.5 Flash or GLM-5.1 have the bigger context window?
Gemini 3.5 Flash has a 1.0M-token context window — 5× the 200k context of GLM-5.1. Enough for entire codebases, books, or multi-document RAG.
Is there a free tier for Gemini 3.5 Flash or GLM-5.1?
Gemini 3.5 Flash: yes — Reduced daily quota via AI Studio for prototyping. GLM-5.1: yes — Free tier with monthly token allowance.
Which is better for coding — Gemini 3.5 Flash or GLM-5.1?
GLM-5.1 leads on coding benchmarks (Gemini 3.5 Flash: 91/100, GLM-5.1: 93/100). For production coding agents also weigh tool-use performance — Gemini 3.5 Flash scores 90, GLM-5.1 scores 86.