Scanners to photograph and record the identity of people entering bars and nightclubs are being introduced to tackle late-night crime.
The plan will allow bar owners to know who is in their club and make it easier to ban people who have caused trouble.
But their use has also raised privacy fears if the databases are not well managed.
The new machines scan and record photo IDs and take a picture of patrons as they enter.
They pick up if a person is under-age, or if they are using fake ID, of if an ID has already been used that night.
"You've got an instant witness list of who could've potentially seen that incident, and that gives the police a starting point if they're launching an inquiry," said Thomas Rawson, a distributor of the ID scanners.
While most people at one nightclub ONE News spoke to were happy to have their IDs recorded, saying it made them feel safer, the privacy commission has raised concerns about identity fraud.
Legal experts also say venues need to know their obligations under the privacy act.
"We're going to have blacklists of people who've got into trouble or whatever, how long is that information going to be held?" said associate professor Gehan Gunasekara, of the Auckland Business School.
"Who is it going to be shared with? Are we going to have secret databases that are being shared with the police? That could come back to hurt young people later in their careers," he said.