Windows 10 apps from the universal Windows Store can be downloaded and installed on up to 10 devices per Microsoft account. That's the word from Microsoft's own store documentation, and it's a big decrease from the 81 device limit that is currently available for Windows 8 and 8.1 apps.
The app install limit was spotted by Jesper Nielsem on his Twitter account this weekend. While most users will likely never reach that 10 device ceiling, it could cause problems with a few users who install the same app on their desktop PC, their Windows 10 tablets, their Windows 10 Mobile smartphone and even their Xbox One when it gets its Windows 10 upgrade later this year.
It's possible that Microsoft could change the app device limit once Windows 10 is officially launched on July 29. We have contacted Microsoft to see if they can reveal more information on this limitation.