GLM 5.3 Flash vs GPT-6 Luna Pro: price, context window and capabilities
GLM 5.3 Flash (z-ai/glm-5.3-flash) from Z.ai and GPT-6 Luna Pro (openai/gpt-6-luna-pro) from OpenAI are both multimodal language models on the OceanToken API. GPT-6 Luna Pro costs less per token than GLM 5.3 Flash: $0.10 against $0.15 per 1M input tokens (33% less), and both charge $0.50 per 1M output tokens. Their context windows are almost the same size, about 1.05M tokens: GPT-6 Luna Pro takes 1,050,000 tokens and GLM 5.3 Flash 1,048,576. Both support tool calling, reasoning, structured outputs and image input; only GLM 5.3 Flash also lists video input; only GPT-6 Luna Pro also lists file input.
Side by side
| Spec | GLM 5.3 Flash | GPT-6 Luna Pro |
|---|---|---|
| Model | GLM 5.3 Flashz- | GPT-6 Luna Proopenai/ |
| Publisher | Z.ai | OpenAI |
| Kind | Text, vision & video | Text & vision |
| Context window | 1.05M tokens1,048,576 | 1.05M tokens1,050,000 |
| Input price | $0.15 / 1M tokens | $0.10 / 1M tokens |
| Output price | $0.50 / 1M tokens | $0.50 / 1M tokens |
| Cached input price | $0.03 / 1M tokens | $0.01 / 1M tokens |
| Cache write price | – | $0.125 / 1M tokens |
| Web search price | – | $0.01 / search |
| Inputs | text, images and video | text, images and files |
| Outputs | text | text |
| Tool calling | Yes | Yes |
| Reasoning | Yes | Yes |
| Structured outputs | Yes | Yes |
About these prices
Which should you choose?
- Choose GPT-6 Luna Pro to spend less per token: 33% less for input than GLM 5.3 Flash, at the same output price.
- Context size does not separate them: both hold about 1.05M tokens.
- Choose GLM 5.3 Flash if you need video input: GPT-6 Luna Pro does not list it.
- Not sure? Call both with the same OceanToken API key and compare them on your own prompts; each request is billed per use from one prepaid balance.
Get API Key GLM 5.3 Flash GPT-6 Luna Pro
Frequently asked questions
Which is cheaper, GLM 5.3 Flash or GPT-6 Luna Pro?
GPT-6 Luna Pro. GPT-6 Luna Pro costs less per token than GLM 5.3 Flash: $0.10 against $0.15 per 1M input tokens (33% less), and both charge $0.50 per 1M output tokens. These are OceanToken starting prices per use; the OceanToken console always shows the current price.
Which has the larger context window, GLM 5.3 Flash or GPT-6 Luna Pro?
GPT-6 Luna Pro, by 1,424 tokens. Their context windows are almost the same size, about 1.05M tokens: GPT-6 Luna Pro takes 1,050,000 tokens and GLM 5.3 Flash 1,048,576.
Can I call both GLM 5.3 Flash and GPT-6 Luna Pro with one API key?
Yes. Both are on the OceanToken API at https://api.oceantoken.ai/v1: one API key and one prepaid balance call either model. Send the model id z-ai/glm-5.3-flash or openai/gpt-6-luna-pro.
Models and publishers
GLM 5.3 Flash · GPT-6 Luna Pro · All Z.ai models · All OpenAI models
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