Are close and x on a popup redundant?

The close button or X on a popup is redundant if it's used for an informative dialog. However, it can be useful if it's used for a confirmation dialog.

1. Are the close button and X on a popup redundant?
2. Why is the Close button an X?
3. Should a modal have a close button?

Are the close button and X on a popup redundant?

Yes, they're redundant.

Why is the Close button an X?

X was commonly used to delete characters in-line, but not to close the program. [x] is a true icon, not representing a letter but representing an action, and only adopted to represent 'close' well after the development of graphics-oriented operating systems.

Should a modal have a close button?

Closing the modal: Always provide a clear close option for users by using a button or an 'x' icon at the top right of the modal.