Additional information to the excellent method of @meta-chuh :

• Firstly, contrary to any other character, you cannot insert NUL characters, either, with any of these 3 ways :

  • Alt + nnn , where n are digits, pressed on the numeric keypad ( OEM encoding )

  • Alt + 0nnn , where 0 and n are digits, pressed on the numeric keypad ( ANSI encoding )

  • Alt + the + ( on Numeric keypad ) + hhhh, where h are hexadecimal chars ( UNICODE encoding ) :

    • The letters, from a to f, typed on the main keyboard

    • The digits, from 0 to 9, typed on the numeric keypad

So, the only way is to use the Character Panel ( Edit > Character Panel ) and, then, to double-click on the first line 0 00 NULL in order to insert a single NUL character, at cursor location

Secondly, the present regex engine of N++, can handle the NUL characters in search, without any trouble, using the regexes :

\0 or \x00 or \x{00} or \x{0000} or \N{NUL} or \c@ or \c

Unfortunately, in replacement, there’s, indeed, no mean to insert a NUL character :-(( A work-around is possible, using a local installation of N++ v6.9.0 and a modified version of the Scintilla library ( SciLexer.dll ). Refer to LAST part of this FAQ post :

https://notepad-plus-plus.org/community/topic/15765/faq-desk-where-to-find-regex-documentation/1

Best Regards,

guy038

you have to use the special copy/paste in np++ for binary, non ascii or mixed contents:

menu bar > edit > paste special > copy binary content
and
menu bar > edit > paste special > paste binary content

if you need it often, you can set a custom keyboard shortcut on copy and paste binary content