Keep a private AI on your phone, offline

On 13 October, Wharton professor Ethan Mollick pointed out that 19 AI models small enough to run on a modern smartphone now beat GPT-4, the model that led the field for a whole year.

You download a model over wifi once, so it answers in airplane mode, using your phone’s own chip.

That makes it the right tool for the jobs you would rather no company saw:

• Private notes. A health worry, a money mess or a family row, sorted into something you can act on.
• A sensitive message. The text to your landlord, your ex or your boss, calmed down before you send it.
• No signal. On a plane, abroad without data, or anywhere the bars drop to nothing.

Pick an app

All three are free and run the model on the phone itself. Store pages read 13 October 2026.

Set it up and test it in airplane mode

1. Free up space first. A model is a single big file: Google’s model page lists the smaller Gemma 4 phone model, E2B, at about 2.6 GB, and a download can fail partway on a full phone.
2. Download on wifi and start with the smallest model the app suggests. A model too big for your phone freezes or crashes; both PocketPal and Edge Gallery have a built-in speed test (a benchmark) that shows what your phone can handle. If the app asks you to sign in to Hugging Face before a download, that account is free.
3. Switch on airplane mode, then ask a test question. If it answers, the model is running on your phone, and this is the one check you can do yourself.
4. Leave off anything that goes online. That means web search, remote servers, LM Link and online Agent Skills, and skip any feedback option, which shares what you send with the app maker. For anything really private, keep airplane mode on while you type.
5. Start a new chat for each job. Phone models hold far less text at once than ChatGPT or Claude, so an old conversation crowds out your new note.

The prompt: sort a note or rewrite a message, privately

Small models follow short, labelled instructions far better than a long, loose brief, so this prompt gives the model one job per run and a tight set-up to fill in.

Pick SORT for a messy note, REWRITE for a message you are nervous about sending, or CHECK to see how a message will land before you change it. Fill in the set-up, paste your text at the bottom, and the model checks its own answer before it shows you.

On an older phone, delete the two jobs you are not using before you paste, so the model only reads the one it needs.

You are my private writing helper, running on my phone with no internet. I use you for notes and messages I would not paste into an online chat, so one wrong name, date or number could cause real trouble. Work only from the text I give you, and never add a fact.

SET-UP (I fill this in)
JOB: [pick one: SORT, REWRITE or CHECK]
WHO IT IS FOR: [e.g. "just me", "my landlord", "my sister after an argument"]
TONE: [e.g. "calm and firm", "warm but short", "plain"]
LENGTH: [e.g. "under 120 words", or "any"]
MUST KEEP: [anything that must stay word for word, e.g. "the date 4 November and the flat number", or "nothing"]
MY TEXT:
[paste the note or message here]

THE JOBS
SORT: Turn my messy note into three short lists. FACTS: what happened or what I know. TO DO: each task with who and when; if either is missing, write "not stated". QUESTIONS: anything open or unclear. Keep my own words where you can.
REWRITE: Rewrite my message for the person above, in the tone I asked for. Keep every fact, date and number exactly as I wrote it. Cut repetition and blame. If the reader would need something my text does not say, write [NEED: what is missing] instead of guessing.
CHECK: Leave the message as it is. Read my message as the person receiving it would. List up to three lines that could land badly, say why in one short line each, and offer a calmer version of each.

HOW TO WORK
1. Read all of MY TEXT once before you write anything.
2. If MY TEXT is empty or JOB is not filled in, ask me one short question and stop.
3. If a line in my text could mean two things, quote it and ask me which I meant.
4. Do the one job I picked, and only that job.
5. Never invent a name, date, number, place or promise. Use "not stated" or [NEED: ...] instead.
6. Short sentences, plain words, no extra headings.

BEFORE YOU ANSWER, CHECK
- Every name, date and number in your answer appears in my text.
- The MUST KEEP items are exactly as I wrote them.
- You stayed within my LENGTH.
Then end with one line: "Least sure about: ..." naming the part I should check myself.

Reading on a computer? Email the prompt to yourself, or open this page on your phone and tap Download .txt.

The honest bit

Try it on tonight’s to-do list

Install one app on wifi tonight, download the smallest model it offers and save the prompt in your phone’s notes app, so it is two taps away when you have no signal. Then switch on airplane mode and run SORT on a note you already have.

Send this page to the friend who never pastes anything personal into ChatGPT.

A few quick questions

Will it work on my old phone?

Maybe, with a small model. PocketPal’s Android page asks for 6 GB of memory (RAM) for smaller models and 8 GB or more for better ones. On iPhone, PocketPal runs on iOS 15.1 or later, the oldest iOS version of the three apps. Start with the smallest model and run the app’s benchmark.

Do these apps cost anything?

All three are free to download and the models are free. PocketPal sells optional add-on personas it calls Pals, which you do not need for the prompt above.