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Nagware (also known as begware, annoyware or a nagscreen) is a type of shareware that persistently reminds (nags) the user to register it, often by paying a fee. It usually does this by popping up a message when the user starts the program, or intermittently while the user is using the application. These messages can appear as windows obscuring part of the screen, or as message boxes that can quickly be closed. Some nagware keeps the message up for a certain time period, forcing the user to wait to continue to use the program.
The intent is generally that the user will register or buy the program to get rid of the trial version's annoyance.
Nagware can also refer to software that requires an optical disc to be inserted into its drive; like with many classic CD-ROM games, and even modern DVD and Blu-ray ROM games as well, since that was a common method for copy protection, though ISO images have circumvented this mechanism to some extent.
Through Windows Update, Microsoft loaded nagware to Windows 7 and 8 to offer free downloads of Windows 10. Microsoft Edge periodically 'nags' the user to use it when Windows 10 detects that Mozilla Firefox or Google Chrome are being installed or made the default internet browser.
Wikipedia intermittently displays begware at the top of pages that turn into overlays upon scrolling down. This occurs throughout the year, increasing in frequency in December.  Although there is a range of user reactions, it is often particularly vexing for users who donate on a regular basis but are still forced to endure the annoyance. This is a problem not easily solved by Wikipedia or other charitable organizations in similar circumstances.
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- "2014-2015 Fundraising Report - Wikimedia Foundation". wikimediafoundation.org. Retrieved 2016-12-13.