Does Notepad++ show all hidden characters?

Yes, it does. The way to enable this depends on your version of Notepad++. On newer versions you can use:

Menu View → Show Symbol → *Show All Characters`

or

Menu View → Show Symbol → Show White Space and TAB

(Thanks to bers' comment and bkaid's answers below for these updated locations.)

On older versions you can look for:

Menu View → Show all characters

or

Menu View → Show White Space and TAB

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In newer versions of Notepad++ (currently 5.9), this option is under:

View->Show Symbol->Show All Characters

or

View->Show Symbol->Show White Space and Tab

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Double check your text with the Hex Editor Plug-in. In your case there may have been some control characters which have crept into your text. Usually you'll look at the white-space, and it will say 32 32 32 32, or for Unicode 32 00 32 00 32 00 32 00. You may find the problem this way, providing there isn't masses of code.

Download the Hex Plugin from here; http://sourceforge.net/projects/npp-plugins/files/Hex%20Editor/

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For non-printing characters, you can do the following:

if you could identify the character, where cursor takes 2 arrow keys to move, just select that character.

do Ctrl-F

now you can count or replace or even mark all such characters

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Yes, and unfortunately you cannot turn them off, or any other special characters. The options under \View\Show Symbols only turns on or off things like tabs, spaces, EOL, etc. So if you want to read some obscure coding with text in it - you actually need to look elsewhere. I also looked at changing the coding, ASCII is not listed, and that would not make the mess invisible anyway.

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No, it does not. At least not natively without pluggins.

Yes, N++ does show almost all non printable char, but not all of them, even with the option "Show all characters" toggled on.

For instance, U+200B or U+FEFF or U+A0 are not displayed, even when toggling ON "Show all char".

https://i.stack.imgur.com/FdcJA.png

Here is what it looks like in N++:

https://i.stack.imgur.com/SiWKI.png

NB: Notepadd++ does "see" those characters, because if you move your cursor with the arrow keys, it will not move for one more keystroke after each dot on line 3. But it doesn't display them, even with "Display all characters" options.

Disclaimer: This question was about spaces, but the title is more broad, and this is the first result on SERPs when searching about "displaying all chars on N++".

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