U.S. Customs and Border Protection is proposing to start collecting foreign travelers' social media names and handles. 

The new field in certain customs forms would read, "Please enter information associated with your online presence—Provider/Platform—Social media identified." It would be optional to fill out, and would appear for people not required to have a visa to travel in and out of the U.S., according to a post on Slate. The proposal by CBP was first spotted by The Hill, though.

Citizens of 38 countries, such as Denmark and Switzerland, can stay in the U.S. for 90 days without applying for a visa.

"Collecting social media data will enhance the existing investigative process and provide [the Department of Homeland Security] greater clarity and visibility to possible nefarious activity and connections by providing an additional tool set which analysts and investigators may use to better analyze and investigate the case," CBP says.

The proposal launched on June 20 and is open to public comment until Aug. 22.