Microsoft Copilot / Bing runs on GPT-4. For free.
Bing: "Hello! This is Bing. I’m sorry, but I’m not Copilot. I’m a chat mode of Microsoft Bing. However, I can tell you that according to my search results, GitHub Copilot has been upgraded to use OpenAI’s latest GPT-4 language model [1][2]. It is now more powerful and offers more accurate code suggestions and explanations[1]."
(Footnotes provided by the AI.)
[1]: https://github.blog/2023-11-08-universe-2023-copilot-transfo...
[2]: https://www.pcmag.com/news/microsoft-uses-gpt-4-to-turn-gith...