On-device AI vs cloud AI in a journal app

Where your words go

With on-device AI, the model runs on your iPhone or iPad and your entry is read there. With cloud AI, the app sends your entry to its own servers or to an AI provider and gets an answer back. Many apps mix both. Day One, for example, says some of its AI features can run on your device with Apple Intelligence. Others run on its servers or through a provider it names as OpenAI. It also says entries in end-to-end encrypted journals are briefly not end-to-end encrypted while AI processes them.

• On device: your words stay on the device for processing
• Cloud: your words travel to a server, so the provider's privacy policy and retention rules matter
• Apple's Private Cloud Compute is a middle path that Apple says keeps user data unavailable to Apple and keeps nothing after it answers

Model size and limits

Phone-sized models are small. Apple describes its on-device model as about 3 billion parameters. Apple says it's good at summaries, picking out names and places and understanding text. It isn't designed to be a chatbot for general world knowledge. Each session holds 4,096 tokens, and Apple counts about three to four English characters per token. That's roughly 12,000 to 16,000 characters, shared by the instructions, your entry and the answer. Cloud models can be much larger, such as the ones Apple runs in Private Cloud Compute for more complex requests.

Devices, languages and connections

On-device AI only works where the hardware supports it. As of October 2026, Apple Intelligence needs an iPhone 15 Pro or later, or an iPad or Mac with M1 or later. iPad mini (A17 Pro) works too. It takes up to 8 GB of storage, or up to 14 GB on some newer models, and works in 16 languages. Cloud AI can run on older phones, Android and the web, but it needs a connection every time.

• Apple's newer speech model for transcription runs entirely on the device, after a one-time download per language
• Day One's transcription, by contrast, needs an internet connection
• Apple notes that some of its own server-side Apple Intelligence features have daily usage limits, and Day One says its AI features do too

The two approaches side by side

These are general patterns. Any single app can differ, so check its privacy policy and help pages.

Questions to ask any AI journal

• Which features run on my device, and which send my words to a server?
• If it uses an AI provider, which one? Does it keep or train on my entries?
• Do I need an account, and can I delete everything myself?
• What still works with no connection?
• Can I turn the AI off and keep my entries exactly as I wrote or said them?
• Which devices and languages does the AI support?

Where Dawn Light fits

Dawn Light is on-device. Apple's speech model writes down what you say on your device, and Plus makes summaries, recaps and Ask answers with Apple Intelligence on your device. There's no account and no server. The trade-offs are real. Plus needs a supported device with Apple Intelligence turned on, and Apple's model turns down some entries about very hard subjects. Those entries stay saved with every word.