Snaps can be directed privately to selected contacts or to a semi-public "Story". The private message photo snaps can be viewed for a user-specified length of time (1 to 10 seconds as determined by the sender) before they become inaccessible. Users were previously required to hold down on the screen in order to view a snap; this behavior was removed in July 2015 The requirement to hold on the screen was intended to frustrate the ability to take screenshots of snaps; the Snapchat app does not prevent screenshots from being taken but can notify the sender if it detects that it has been saved. However, these notifications can be bypassed through either unauthorized modifications to the app or by obtaining the image through external means. One snap per day can be replayed for free. In September 2015, Snapchat introduced the option to purchase additional replays through in-app purchases. The ability to purchase extra replays was removed in April 2016.