Who else can read your prompts?

ChatGPT prompts go to OpenAI's servers and may be stored or reviewed. On-device AI keeps the entire conversation inside your phone - the real difference.

Where a prompt actually goes

When you message ChatGPT, the text leaves your phone, crosses the internet, and lands on OpenAI's infrastructure, where the model actually lives and works. Depending on settings and policies, prompts can be retained for a while, reviewed for safety, or used to improve the service over time. You are, quite literally, having the conversation on someone else's computer, far outside your control.

What changes on-device

Run the model on your own phone and the journey disappears. In Local AI the model file sits in local storage, inference happens on your chip, and the conversation never touches a network - it works in airplane mode because there is nothing to connect to. There is no account either, so no identity is attached to what you ask.

The honest trade-off

Privacy is not free, though. Frontier cloud models are far bigger than anything a phone can carry, so the hardest reasoning and the most current knowledge will still favor the cloud. On-device models handle everyday writing, summarizing and chatting perfectly well, but if you need the absolute strongest possible answer and the question is not a sensitive one, the cloud sometimes still wins.

A practical split

Plenty of people end up using both, and that is a sensible split. Cloud chat for the questions you would happily say out loud in public; on-device AI for the rest - journal entries, work drafts, health questions, anything about money or family. A useful rule: if you would not paste it on a public forum, keep it on the phone.