The ChatGPT API is not free. OpenAI operates on a pay-as-you-go payment model, which means you'll be charged based on your usage. The cost of using the API depends on factors like the number of tokens processed, the model you choose, and the amount of computation required. While OpenAI might offer trial funds for new users ($5 on sign-up, available for 3 months), these funds are limited and will eventually be depleted. For detailed pricing information, you can check OpenAI's pricing page.