Arduino Uno - Access Denied while Uploading


I went to upload my sketch to my Uno (r3), but unusually, the Upload Console returned this error:

avrdude: ser_open(): can't open device "\.\COM4": Access is denied.

Just started seeing this, cannot upload.

Please always post the complete compiler error text, in code tags (</>).

Do you have the correct com port selected? Check in the Tools menu.