A money saving app for Android that never asks for your bank

Nearly every money saving app on Google Play begins the same way: create an account, then hand over read access to your bank so the app can categorize what you already spent. Keep the Diff needs no account, and it cannot connect to your bank because there is no bank integration in it at all.

Keep the Diff also records something an expense tracker cannot see. An expense tracker only shows you money leaving, so the decisions that stop money leaving are invisible to it, even though they are the whole reason there is anything left at the end of the month.

What the app does

You log two numbers: what you were ready to spend, and what you actually spent. The difference is the Diff, and it is recorded as money you kept. The Diff adds up by week, by month, and toward whatever you are saving for. Logging a decision takes three taps.

Buy the thing anyway and nothing happens. There is simply no Diff that time. No budget to exceed, no streak to break, and no red number, because the lowest a week can read is zero.

Spent less than you planned? You still get a Diff. Ninety dollars planned and forty spent is a fifty dollar Diff.

On Android specifically

• A real Android app, built with Jetpack Compose and laid out for Android from the start.
• Home screen widgets. This week's Diff on the home screen, and a widget for each goal with its photo and how far along it is, so the total is in front of you without opening the app.
• Wear OS. Log a Diff from your wrist, and put a goal on your watch face to see how close it is. Every screen scrolls inside the round display, so nothing is cut off at the edge.
• Log a Diff from anywhere. Press and hold the app icon for shortcuts, or add Log a Diff to Quick Settings.
• Phones, tablets, Chromebooks and Googlebook OS. On a tablet or a laptop the content holds a single reading column, so the line length stays readable, and the app works with a keyboard and trackpad as well as touch.
• Only the permissions the app uses. Biometric unlock for App Lock, notifications and exact alarms so a planned check-in arrives on time, and a wake lock. No location, no contacts, no SMS, no accessibility service. The one file the app ever reads is a single photo, and only if you attach one to a goal yourself.
• The app works offline, permanently. There is no offline mode to switch on. Everything you log is written to the device first, so a plane, a basement or a dead SIM changes nothing about what the app can do.

Your numbers stay yours

No account needed, no analytics, no tracking and no advertising identifier. Everything you log is written to the app's own private storage on your device. The app talks to the internet only when you buy Premium, which Google Play handles, or if you turn on sync, which sends a copy sealed with a key only your devices hold. We never see anything you log.

If your phone backs itself up through Google, your Keep the Diff data is included in the backup the same as any other app's data. That backup is yours, and we cannot see inside it. The full privacy policy is one page and says the same thing at greater length.

Free, and what Premium adds

Logging decisions is free, with no ads and no limit. So is this week's total, this month's, your recent history, the weekly recap card, milestones with a card to share, and what this pace adds up to over a year.

Premium adds your full history with CSV export, categories and breakdowns, unlimited goals with a photo of the thing you are saving for, about when you will reach each goal at your recent pace, recurring Diffs for a subscription you canceled or downgraded, home screen widgets with one for each goal, and the Wear OS app. One subscription covers every device you own. See Premium pricing.

New in 1.2.7

• Premium Lifetime. Pay once for every Premium feature, now and later, on up to 10 devices.
• Sunday recap. Every Sunday at 6 pm, a short note of what you kept that week. You can turn it off in Settings.
• Rate and share. Rate Keep the Diff or share it with a friend, right from Settings.
• Sign in with Microsoft. Use your Microsoft account to sign in, so Premium follows you to every device.

Also on your other devices

The same app runs on iPhone, iPad and Apple Watch, and on Mac, Windows and Linux as a direct download. One Premium subscription covers every device you own.

Try it in your browser first if you would rather not install anything, or read what to look for in a no spend challenge app.