Download
No account, no email address, no sign-up.
The download below is the whole of it. Run the installer, open OWL, and you're looking at a budget.
About 17 MB. OWL is in beta: builds change often, so the version you get is the newest one.
OWL for Android
The phone app installs straight from here; about 110 MB. Your phone will ask permission to install apps from the browser the first time, and Play Protect may add its own caution for the same reason Windows does: a small beta has not been seen many times before. An iPhone app follows, and macOS after that. No dates here until they are true.
What it needs
Any computer that runs Windows 10 runs OWL.
If Windows warns you
Windows sometimes cautions against installers it has not seen many times before, and a small beta has not been seen many times before. If SmartScreen appears, “More info” and then “Run anyway” will proceed. Only ever do that for software you got from this page.
What happens first
OWL opens, you type what your bank account holds, and you are budgeting inside a minute. That is the whole setup. Everything stays on your computer, and Settings has a one-click backup whenever you want a copy of your own.