ChatGPT offline on iPhone: what works without internet

Updated

Short answer: ChatGPT doesn't work offline. If you want AI chat on a plane, on the subway or with no signal, you need an app that runs its model on the phone. Here's the difference, and where Castmates fits.

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Why ChatGPT stops without a connection

The ChatGPT app is a window onto a model that runs in a data centre. Each message goes up, the reply comes back down. With no signal there's nothing to answer you, and no setting changes that. The same is true of most popular chatbot apps.

What does work with no internet

Anything that keeps the model on the phone. Your iPhone's chip generates the reply itself, so airplane mode makes no difference. The trade-off is size: a model small enough to live on a phone is far smaller than the ones behind cloud chatbots. Some local apps use that for general questions and summaries. Castmates uses it for something narrower.

Where Castmates fits

Castmates is for talking to characters, not for asking an assistant to research something. You get a cast of 35 characters who stay in role, and the story keeps going whether or not you have a signal.

What you give up compared with ChatGPT

A fair way to choose

If you need answers, drafts or code offline, look at a general-purpose local app. Our comparison of offline AI apps lays out the options. If you want a character to talk to on a flight, here is how a local AI app works on iPhone, and you can meet the cast before installing.

Frequently asked questions

Does ChatGPT work offline on iPhone?
No. The ChatGPT app sends your message to OpenAI's servers and shows what comes back, so with no connection it can't answer. Past chats you've already loaded may still be readable, but you can't get a new reply.
Is there any AI chat that works without internet on iPhone?
Yes, apps that run a small model on the phone itself. Castmates is one, built for character chat. After a one-time download of about 2 GB it works in airplane mode. Some other apps run general-purpose local models for questions and summaries.
Which iPhones can run Castmates offline?
iPhones with 6 GB of RAM or more. The iPhone 11, 12, 13, 13 mini and SE have 4 GB and can't run it. Check your model under Settings, General, About.
Is an offline AI as good as ChatGPT?
No, and it's not trying to be. A 2 GB model on a phone is much smaller than the models behind ChatGPT, so it's weaker at research, coding and long documents. Castmates is tuned for staying in character in a story, which is a narrower job.
Do I need an account for the offline mode?
No. There's no sign-in. You install the app, let the model download over Wi-Fi once, and start talking to a character.
Are my chats sent anywhere?
No. Replies are generated on your iPhone and chats are stored only on the phone, not on our servers. That also means deleting the app deletes them, unless you restore the phone from a backup.

Try Castmates free

35 characters, 127 scenarios, and every conversation stays on your iPhone.