Besides the two data downloads and the online activity log that Facebook highlights, other personal information can be found in the account settings, Schrems said. "A normal user is entitled to get everything from Facebook. Today, users have to hunt all over Facebook to get it."
The way the download tool and the extended archive work make it hard to check if all the information Facebook has is made available to the user, said Schrems. "Right now, Facebook is just gathering some information from the raw format and transfers it into some HTML download thing," he said. "Facebook is just not including the data that is a problem for them."
Schrems estimated that Facebook now only provides him with half of his personal data via the download tools, compared to the earlier raw file he and other early requesters received. "Only we can prove that the other half is not there because we have the original raw format," he said.
Facebook declined to discuss the missing data or the Irish commissioner's forthcoming audit.
"We believe that every Facebook user owns his or her own data and should have simple and easy access to it," a company representative said in an emailed statement, adding that is why the company has built a way for users to "download everything."
"People who want a copy of the information they have put on Facebook can click a link located in 'Account Settings' and easily get a copy of all of it in a single download," the statement said.
Loek covers all things tech for the IDG News Service. Follow him on Twitter at @loekessers or email tips and comments to firstname.lastname@example.org