OpenAI ChatGPT 4o is continually updated by OpenAI to point to the current version of GPT-4o used by ChatGPT. It therefore differs slightly from the API version of GPT-4o in that it has additional RLHF. It is intended for research and evaluation.
OpenAI notes that this model is not suited for production use-cases as it may be removed or redirected to another model in the future.