ChatGPT users can enable a setting to continue accessing legacy models like o3 and GPT-4o

ChatGPT now defaults to GPT-5 automatically selecting the model for each task, which may help beginners but feel less transparent to advanced users. A setting is still available to enable access to older "legacy" models such as o3 and GPT-4o. When turned on, these can be manually chosen from the "Other models" menu. This manual option applies only to past models. The GPT-5 "Thinking" and "Pro" versions can also be selected manually, but only by Pro subscribers.