By default Windows does not allow to copy the text from open Window, but it can be done with a freeware and portable tool GetWindowText. Textify also allows you to copy the text but from Dialog boxes.
How to copy text from open windows with GetWindowText?
If you have a folder or program window open and you want to copy the text, you can do so easily using this freeware GetWindowText tool.
1. Left click from mouse-button on the GetWindowText icon on the left side and by holding down it drag on the Window from where you want to read / copy the Text.
2. When you release the mouse button, the reading will be finished. The text will appear in the textbox of GetWindowText tool which you can copy by selecting it.
This freeware software can read almost all the texts from Edit, Static, Groupbox Controls, and so on. It also supports directory trees (SysTreeView32), Combobox, and list views (SysListView32) to read the entire contents.
GetWindowText is compatible with all version of Windows including Windows 10 / 8 / 7 / Vista and Windows XP and supports x64 and x32 operating systems too. You can download GetWindowText from here.
JOCR is an another useful app that allows you to copy texts from scanned documents in Windows 10/8/7. Gttext is another useful app that lets you copy Error Codes & Messages from Dialog Boxes In Windows 10/8/7.