What Splitsheet keeps
Splitsheet has no accounts, so it knows almost nothing about you. This page says exactly what it does hold, and why.
What is stored
For each sheet: the name you gave the group, the first names you typed for the people in it, and the lines — what was bought, how much, in which currency, who paid, and who it was for. That is all. No email address, no phone number, no bank or card details, and no name beyond what somebody typed themselves.
The link is the key
Each sheet has a long random address, and holding that address is what lets you read and write the sheet. It works like a shared calendar link. That also means the link is worth guarding: anyone you send it to can see the sheet, and there is no way to take it back from somebody who already has it. If a sheet gets out, start a new one.
What stays on your device
The name you choose for yourself, and the list of sheets this browser has opened, are kept in the browser and never sent anywhere. Clearing your browser data removes them; the sheet itself is unaffected.
No money, ever
Splitsheet does the arithmetic and nothing else. It has no connection to any bank, card or payment service, it cannot move money, and it will never ask for the details that would let it.
Measurement
Pages are counted so we know whether the tool is being used, and you are asked before anything beyond a plain count is collected. Amounts, names and sheet contents are never part of that.
Questions
Write to hei@pixygon.io and a person will answer.