Suggestion: If you don’t know what a plugin is doing, perhaps uninstall it.

Why is a \n appended at the end of my .txt file

It depends on whether you mean “why is it just LF when I am set to windows CR LF?” or whether you mean “why is there a newline sequence appropriate to my settings (either \n for linux LF, or \r\n for windows CR LF) at the end of my file, when I didn’t actually type an ENTER at the end of my file?” Because one is the question that @Terry-R answered, the second is my guess — oh, while answering this, I see you’ve continued the conversation, and I believe my guess is probably correct.

NppEditorConfig (0.4)

You have the NppEditorConfig plugin. For the active file, does Plugins > Editor Config > Show EditorConfig settings for this file show insert_final_newline = true ? if so, then your .editorconfig file (either in the active directory or one of its parents) sets it so that the plugin automatically adds the newline

So, assuming my guess is correct, it looks like you probably told the NppEditorConfig plugin to add newlines, then blamed it on Notepad++. (edit: or, alternatively, the repo that you have a checkout in which you are editing a file in had a .editorconfig that you didn’t know about, so your working copy started correctly honoring that repo’s settings once you installed the NppEditorConfig plugin – so maybe it was without your knowledge, but still because you have the plugin)

You said appended, so ONLY the (second to) last line has this?

Can you think of any change you have made recently to either your file itself, or configuration changes in Notepad++.

How about opening a new file and type a single line and press enter to get the EOL type it thinks should be there. Post back what you saw.

Terry

I am on Windows, never Linux. So not touched there.

I can fix it, but as soon as I save it, it returns.

Notepad, does not do that!!
And np++ did not before

Why is a \n appended at the end of my .txt file

\n is used by a Linux (Unix) system. Has the file been altered by any Linux system in the interim?

Once you have it opened in Notepad++ you can fix this by using the Edit, EOL Conversion and select Windows (CR/LF). If that is dimmed, then select one of the others, then repeat and select the Windows one again. That will fix it.

Terry