Z.ai Free tierOpen weights

GLM-5.1

GLM-5.1 is a GLM model from Z.ai, released in 2026-04. It costs $1.4 / $4.4 per 1M, has a 200k-token context window, and is best for coding, cheap-frontier, open-weights. Last verified 2026-05-22.

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Spec sheet

Pricing

Input
$1.4 / 1M
Output
$4.4 / 1M
Cached input
$0.26 / 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
Yes
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
$54.40
per month
100k calls/mo
$544.00
per month
1M calls/mo
$5.4k
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 GPT-5.4 Minivs Qwen3-Maxvs Claude Haiku 4.5vs Gemini 3 Flashvs Grok 4.3vs Gemini 3.1 Flash-Lite

FAQ — GLM-5.1

How much does GLM-5.1 cost?

GLM-5.1 costs $1.4 / $4.4 per 1M tokens on the Z.ai API. Cached input reads cost $0.26 per 1M, cutting the input bill by roughly 81% on repeat system prompts.

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.