GLM-5.1 vs Grok 4.20
GLM-5.1 and Grok 4.20 are both current production-tier models. GLM-5.1 is meaningfully cheaper at $1 / $3.2 per 1M. Grok 4.20 has a 2M context window — about 10× the 200k of GLM-5.1. GLM-5.1 leads on multilingual. Grok 4.20 leads on long-context retrieval, instruction following.
Specs side by side
| Metric | Z.ai GLM-5.1 | xAI Grok 4.20 |
|---|---|---|
| Input price (per 1M) | $1 | $2 |
| Output price (per 1M) | $3.2 | $6 |
| Context window | 200k tokens | 2M tokens |
| Speed tier | balanced | balanced |
| Open weights | Yes | No |
| EU region | No | No |
| Free tier | bigmodel.cn | No |
| Prompt caching | No | Yes |
| Vision input | No | Yes |
| Extended thinking | Yes | Yes |
When to choose each
Choose GLM-5.1 if…
- Cost is a priority ($1 / $3.2 per 1M vs $2 / $6 per 1M)
- You need open weights for self-hosting or fine-tuning
- You want a free tier for prototyping
- Multilingual is central to your workload
Choose Grok 4.20 if…
- You need 2M context (10× more than GLM-5.1)
- You need image input / vision
- Long-context retrieval is central to your workload
- Instruction following is central to your workload
Benchmark delta
GLM-5.1 leads on
- Multilingual
Grok 4.20 leads on
- Long-context retrieval
- Instruction following
FAQ — GLM-5.1 vs Grok 4.20
GLM-5.1 vs Grok 4.20 — which is better?
GLM-5.1 and Grok 4.20 are both current production-tier models. GLM-5.1 is meaningfully cheaper at $1 / $3.2 per 1M. Grok 4.20 has a 2M context window — about 10× the 200k of GLM-5.1. GLM-5.1 leads on multilingual. Grok 4.20 leads on long-context retrieval, instruction following. The right pick depends on your use case — see "When to choose each" above for a data-driven decision.
How does GLM-5.1 pricing compare to Grok 4.20?
GLM-5.1 costs $1 / $3.2 per 1M vs Grok 4.20 at $2 / $6 per 1M. GLM-5.1 is cheaper on output tokens by roughly 87%. Both support prompt caching, which reduces effective cost by 80-90% on repeat system prompts.
Does GLM-5.1 or Grok 4.20 have the bigger context window?
Grok 4.20 has a 2M-token context window — 10× the 200k context of GLM-5.1. Enough for entire codebases, books, or multi-document RAG.
Is there a free tier for GLM-5.1 or Grok 4.20?
GLM-5.1: yes — Free tier with monthly token allowance. Grok 4.20: no — X Premium includes Grok web chat; API is paid.
Which is better for coding — GLM-5.1 or Grok 4.20?
GLM-5.1 leads on coding benchmarks (GLM-5.1: 93/100, Grok 4.20: 91/100). For production coding agents also weigh tool-use performance — GLM-5.1 scores 86, Grok 4.20 scores 88.