How to Get Free GLM-5.3 API Access

Looking for a flagship model with a massive context window and no credit card? GLM-5.3 is free right now through ZenMux.

You get 1M tokens of input context, up to 128K output tokens, and full tool calling and MCP support, priced at $0 per million tokens in and out.

Tutorial

1. Open http://zenmux.ai and create a free account.
2. Generate an API key from the dashboard.
3. Set your Base URL to http://zenmux.ai/api/v1.
4. Select the model ID z-ai/glm-5.3-free and start routing calls. This model handles tool calling and MCP out of the box.
5. Open https://chat.z.ai to test GLM-5.3 in your browser. Use it to check the model's output before wiring up your API calls.

Wrapping Up

You now have a free flagship model with a 1M token context for coding and long-horizon tasks. The promotional endpoints can change quickly, so run your tests while the offer is live.