Z.ai Free tierOpen weights

GLM-5.1

GLM-5.1 is a GLM model from Z.ai, released in 2026-04. It costs $1 / $3.2 per 1M, has a 200k-token context window, and is best for coding, cheap-frontier, open-weights. Last verified 2026-04-19.

Try GLM-5.1 Docs Take the picker quiz

Spec sheet

Pricing

Input
$1 / 1M
Output
$3.2 / 1M
Free tier
bigmodel.cn

Context & speed

Context window
200k tokens
Max output
131k tokens
Throughput
~95 tok/s
Time to first token
~700 ms
Speed tier
balanced

Capabilities

Tool use
Yes
Structured output
Yes
Prompt caching
No
Extended thinking
Yes
Vision input
No
Audio in / out
No
Fine-tuning
Yes

Deployment

Open weights
Yes
On-prem
Yes
HIPAA eligible
No
Zero retention
No
Regions
apac, us

Estimated monthly cost

Assumes typical token shape: 2k input, 600 output per call. Prompt caching is excluded from these figures.

10k calls/mo
$39.20
per month
100k calls/mo
$392.00
per month
1M calls/mo
$3.9k
per month

When to use GLM-5.1

Sweet spot

  • coding
  • cheap frontier
  • open weights
  • multilingual

Known trade-offs

  • data-routing via China for hosted API
  • newer SDK ecosystem

Best use cases

Best LLM for On-prem

Open-weights frontier model; top SWE-Bench Pro + 744B MoE arch

Works with

Z.ai SDKOpenAI-compatible APIOpenRouterOllamavLLMLangChain

Compare GLM-5.1 to other models

vs Gemini 3 Flashvs Qwen 3.6 Plusvs o4-minivs GPT-5.4 Minivs Gemini 3.1 Flash-Litevs Claude Haiku 4.5

FAQ — GLM-5.1

How much does GLM-5.1 cost?

GLM-5.1 costs $1 / $3.2 per 1M tokens on the Z.ai API. This model does not currently support prompt caching, so list price is the full cost.

What is the context window of GLM-5.1?

GLM-5.1 has a 200k-token context window with up to 131k tokens of output. That's enough for long reports, extended chat histories, or structured document analysis.

Does GLM-5.1 have a free tier?

Yes — Free tier with monthly token allowance. Start at https://bigmodel.cn.

Is GLM-5.1 HIPAA / EU / on-prem friendly?

GLM-5.1 is not HIPAA-eligible, not available in an EU region, and offers open weights for self-hosting. Zero data retention is not available.

What is GLM-5.1 best for?

GLM-5.1 is best for coding, cheap frontier, open weights, multilingual. Trade-offs to be aware of: data-routing via China for hosted API; newer SDK ecosystem.

Which tools and SDKs work with GLM-5.1?

GLM-5.1 integrates with Z.ai SDK, OpenAI-compatible API, OpenRouter, Ollama, vLLM, LangChain. Most major AI frameworks support it either natively or through OpenAI-compatible endpoints.