How to Run an LLM on iPhone: A Step-by-Step Guide

Here is how to run an LLM on iPhone: install an app that runs models on the device, pick a model that fits your iPhone’s memory, download it once over Wi-Fi, and start chatting. After that, every answer is generated on your phone, even in airplane mode. This guide walks through each step with Priobs as the example.

Why run an LLM on your iPhone

Most AI apps send your text to a data center and wait for the answer. Phones are now fast enough, and models small enough, that a lot of that work can happen in your pocket instead.

• Your prompts stay on your iPhone. Local generation never sends them to a server.
• It works without internet. Once the model is downloaded, airplane mode changes nothing.
• No Priobs account. You don’t sign up to chat.
• No queue. Your iPhone starts answering the moment you hit send.

What makes it possible: MLX and quantization

Priobs uses Apple’s MLX framework, a machine learning library built for Apple Silicon, to run models on the iPhone’s CPU and GPU.

The other half is quantization. Models are usually stored at a precision a phone can’t handle. Quantization compresses them, commonly to 4 bits, which shrinks both the file and the memory it needs with only a small hit to quality. Every open model in Priobs is a 4-bit MLX build for that reason.

What you need

Two things decide whether a model runs on your iPhone: iOS version and RAM.

iOS. Priobs needs iOS 26 or later.

RAM. Each model needs a minimum amount of memory, and iOS gives a single app only part of your iPhone’s total RAM. Here is the full library:

You don’t have to work this out yourself. Priobs hides models your iPhone doesn’t have the memory for, marks ones close to the limit as “may be unstable”, and recommends one for your device.

How to run an LLM on iPhone, step by step

Step 1: Install the app

Priobs is free to download on the App Store and comes with a free trial. The app itself is under 60 MB. The models are what take real space, and you download those separately. To keep chatting after the trial, you need a Priobs Pro subscription.

Step 2: Pick a model

Open the model library in the app. You will see every model your iPhone can run, each labeled with what it is good at, and one marked as recommended for your device. If you are unsure, take the recommendation. Want to compare first? Our guide to the best local LLM for iPhone goes through every option.

Step 3: Download it over Wi-Fi

Models range from 288 MB to 3.6 GB, so use Wi-Fi and check your free storage first. Downloads are pinned to a fixed model version and checked with a SHA-256 hash, so you get exactly the file you expect.

Step 4: Start chatting

Select the model and type, or dictate. Dictation also runs on the device. Turn on airplane mode if you like: the answer still comes. Leave the app mid-answer and it keeps generating in the background.

Step 5: Try Apple Intelligence too (optional)

On iPhone 15 Pro or newer with Apple Intelligence turned on, Apple Intelligence appears in the same library with nothing to download. It’s included with Priobs Pro, so compare it with an open model and keep whichever you like. The details are in Apple Intelligence vs local LLMs.

Go further: files, tools and automations

Once your local LLM runs, it can do more than chat.

Attach files. Add a PDF, Word document, Excel sheet, PowerPoint deck or a photo. Priobs extracts the text on your iPhone, so you can summarize a PDF or ask questions about a contract with no connection at all. Photos are read with on-device text recognition. The model reads the text in a screenshot or scan. It doesn’t see the image itself.

Switch on tools. Models with tool support can read and add calendar events and reminders, look up contacts and birthdays, and answer questions about your steps, sleep or workouts from Health. Each tool is a separate toggle and stays off until you turn it on.

Automate prompts. Schedule a prompt, like a morning briefing, or run one before a calendar event. The answer arrives as a notification.

Use Siri and Shortcuts. Say “Ask Priobs” to get an answer in the background, or start a chat and run automations from Shortcuts.

Search your library. Find any past chat or attachment by what it says.

Web search, if you want it. Add your own Brave Search API key and a model can look things up. It is off by default, asks before every search, and only the search query goes to Brave.

What to expect: the honest limits

Local models do well at:

• Everyday questions and chat
• Drafting and editing emails, messages and short documents
• Brainstorming and explaining ideas
• Summarizing text and documents you attach
• Basic coding help

Cloud models still win at:

• Very long documents or huge amounts of context at once
• The hardest specialist reasoning
• Anything that needs a model far bigger than a phone can hold

If most of your use sits in the first list, a local model on a modern iPhone will feel more than capable. More on that in on-device AI vs cloud AI.

Planning to use it offline?

Download your models before you lose signal, then send one test message. Our guide to offline AI on iPhone covers what works without internet and what still needs a connection.

The bottom line

Running an LLM on an iPhone is practical today for most everyday AI use. Pick a model that fits your iPhone, download it once, and you have an assistant that answers on your phone with or without signal. Questions about devices or pricing? The FAQ has the answers. See how Priobs works.