How to use OpenAI's GPT-5 API for free

Vercel’s AI Gateway is a unified interface for interacting with multiple LLMs across different providers.

Right now, you can get access to more than 150+ LLM models from them.

Apparently, they’re providing $5 per month free credit which you can use to try any LLM model including OpenAI’s GPT-5.5

How to get started?

Get your API key for AI Gateway from your Vercel Dashboard..

Once you have the key, you can set the base URL and API key in an SDK that supports OpenAI, or you can directly interact with it via cURL.L

Example

curl -X POST "https://ai-gateway.vercel.sh/v1/chat/completions" \
-H "Authorization: Bearer $AI_GATEWAY_API_KEY" \
-H "Content-Type: application/json" \
-d '{
  "model": "openai/gpt-5",
  "messages": [
    {
      "role": "user",
      "content": "Why is the sky blue?"
    }
  ],
  "stream": false
}'

Happy building-with AI!