The new GPT-5 is now the default model for all logged-in ChatGPT users, and it replaces the previous version. The company is retiring some older models. This includes GPT-4o, GPT-4.1, GPT-4.5, GPT-4.1-mini, o4-mini, o4-mini-high, o3, and o3-pro. Any ongoing conversations that were using these models will now automatically shift to their GPT-5 equivalent.