In your browserVersion 1.0.1
Spreadsheet pseudonymizer
Drop a CSV. Pick the columns that identify people. Get the same data back with those values replaced by consistent pseudonyms, so the rows still join and nobody is named. The file never leaves your computer.
Load a spreadsheet
Settings
Result
The key file maps every token back to the original value. Anyone holding it can undo the pseudonymization. Keep it where you keep the original data.
How the two modes differ
Keyed hash HMAC-SHA256 over the value with a key derived from your passphrase (PBKDF2, 100,000 rounds).
Same passphrase on a different file gives the same pseudonyms, so files can still be joined.
Without the passphrase the pseudonyms cannot be reversed. There is no key file to lose.
Tokens Values become NAME-0001, NAME-0002 in order of first appearance. Readable, but only
consistent within one run, and reversible by anyone holding the key file.
Risk check Columns you did not pseudonymize can still single people out together (postcode plus
date of birth plus sex is the classic case). The tool counts rows that are unique on
the remaining columns and warns you. It is a warning light, not a guarantee.