gpt-oss-20b is an open-weight 21B parameter model released by OpenAI under the Apache 2.0 license. It uses a Mixture-of-Experts (MoE) architecture with 3.6B active parameters per forward pass, optimized for lower-latency inference and deplo…
Model details →OpenAI: gpt-oss-20b (free) vs Z.ai: GLM 4.5 Air (free)
OpenAI: gpt-oss-20b (free) and Z.ai: GLM 4.5 Air (free) are evenly matched on 6 axes — pick the one whose provider, latency, or licensing fits your stack.
GLM-4.5-Air is the lightweight variant of our latest flagship model family, also purpose-built for agent-centric applications. Like GLM-4.5, it adopts the Mixture-of-Experts (MoE) architecture but with a more compact parameter size. GLM-4.5…
Model details →Side-by-side comparison
| Capability | OpenAI: gpt-oss-20b (free) | Z.ai: GLM 4.5 Air (free) | Winner |
|---|---|---|---|
| Context window Maximum number of input tokens the model can attend to in a single request. | 131K | 131K | Tie |
| Input price (per 1M) Cost per million input tokens billed by the provider. | $0.00 | $0.00 | Tie |
| Output price (per 1M) Cost per million output tokens billed by the provider. | $0.00 | $0.00 | Tie |
| Tool / function calling First-class support for emitting structured tool calls. | Yes | Yes | Tie |
| Vision input Accepts image inputs alongside text. | — | — | Tie |
| Reasoning mode Internal chain-of-thought / extended-thinking support. | Yes | Yes | Tie |
Frequently asked questions
Is OpenAI: gpt-oss-20b (free) better than Z.ai: GLM 4.5 Air (free)?
OpenAI: gpt-oss-20b (free) and Z.ai: GLM 4.5 Air (free) are evenly matched on 6 axes — pick the one whose provider, latency, or licensing fits your stack.
What's the price difference between OpenAI: gpt-oss-20b (free) and Z.ai: GLM 4.5 Air (free)?
Input: $0.00 vs $0.00 per 1M tokens. Output: $0.00 vs $0.00 per 1M tokens.
What context windows do OpenAI: gpt-oss-20b (free) and Z.ai: GLM 4.5 Air (free) support?
OpenAI: gpt-oss-20b (free) supports up to 131K tokens. Z.ai: GLM 4.5 Air (free) supports up to 131K tokens.
Do both OpenAI: gpt-oss-20b (free) and Z.ai: GLM 4.5 Air (free) support tool calling?
OpenAI: gpt-oss-20b (free): yes. Z.ai: GLM 4.5 Air (free): yes.