Switch to Extended search mode in the Replace dialog.
Find what: rnrn
Replace with: (leave this blank)
Press Replace All. All the blank lines are gone.
* rn is a newline character (in Windows).
* rnrn finds two newline characters (what you get from pressing Enter twice).
2 thoughts on “Remove Blank Lines in a Document With Notepad++ With Extended Search Mode”
Excellent! Just used this…much appreciated.