When ChatGPT suddenly answers in English, the account is usually fine — one of three things has changed: the app language setting, the conversation context, or the browser language. Work through them in order and most cases are fixed in three minutes.
Step 1: Check the app language setting
Open the language option in settings and confirm it has not switched to English. Many people find it reset to the default after an app update or signing in on a new device. After switching back, start a new conversation to test — the old conversation's language habits linger.
Step 2: Say so in a new conversation
Write “Please answer entirely in Chinese” as the first line of a new conversation. If the previous conversation contained lots of English material, code, or English questions, the model follows the conversation language and keeps answering in English. That is not a bug; it is following context.
Step 3: Check browser and system language
Web users should also check browser language and translation extensions: when the browser's preferred language is English, parts of the interface and answer tendencies follow. Move Chinese to the preferred language, turn off auto-translation for that page, and refresh.
Two cases that are not faults
One is when the question itself involves English terms, code, or English literature — mixed English is normal there. The other is an occasional English sentence, normal output variation; just ask it to repeat in Chinese. Only if every conversation on every device turns English should you consider account region or network issues.
