Keep the Diff Download
All articles

An app for logging the money you didn't spend

By , who built Keep the Diff

The app you want is a savings tracker that counts the purchases you skip. When you decide not to buy something, or spend less than you planned, you write down the amount you did not spend, and the app adds it to a running total. Keep the Diff does exactly this, for free, on iPhone, Android, Mac and Windows.

Most money apps only count what leaves your account. A skipped purchase leaves no trace in a bank feed, so a budget app has nowhere to put it. A savings tracker records the decision itself.

How it works, with real numbers

Say you were about to order takeout for $32 and cooked at home instead, for about $8 of groceries. You log two numbers: what you were ready to spend ($32) and what you actually spent ($8). The difference, $24, goes on your total.

Later that week you walk past a $60 pair of shoes and leave them on the shelf. You log $60 ready to spend and $0 spent. Your total is now $84.

Keep the Diff calls that difference the Diff. Each one takes a few seconds to log, and the app keeps them as a weekly total, a monthly total and an all time total.

Free ways to do the same thing

You do not need an app to start. Any of these works:

  • A note on your phone. One line per decision: the item, what you were ready to spend, what you spent. Add up the last column at the end of the month.
  • A spreadsheet. Three columns and a sum. You can sort by month and see which kinds of purchases you skip most often.
  • A transfer. Each time you skip something, move the same amount into a savings account. The balance is your total, and the money is already put away.

The note and the spreadsheet are easy to forget once the habit is new. An app helps because it sits on your Home Screen and takes one tap to open.

What Keep the Diff adds

  • One tap to log. From the app, a Home Screen widget, a shortcut on the app icon, your watch, or the menu bar on a computer.
  • A goal with a photo. Name what you are saving for and add a picture. Each Diff can count toward it.
  • A check-in later. If you plan to spend less on something, the app asks afterward how it went, so you log the real number.
  • No bank connection and no account. Your entries stay on your device unless you turn on sync.

Logging, the running total and a goal are free. Premium adds full history, CSV export, more goals, categories, recurring Diffs, sync and App Lock.

Questions

Does it count money I never had to spend? It counts what you decide counts. If you were genuinely ready to buy something and chose not to, log it. If you were never going to buy it, leave it out, and the total stays honest.

Is the total money in a bank account? No. It is a record of what you kept. If you want the money set aside too, move it to savings when you log it.

What if I buy it anyway? Nothing is lost. You can log the purchase with what you spent, and the total keeps everything you already kept. See what to do when you buy it anyway.

Does it need my bank details? No. Keep the Diff never connects to a bank.

To see the numbers move, try Keep the Diff in your browser, or read how much you actually save by not buying.

More on this