Switching to tabs to the right or left of the current tab in Notepad++

Update

The functionality is included by default in Notepad++ v6.4.5 and later. 6.4.5 was released August 9th 2013. Note the current version is 7.5.8 released July 23rd 2018.

If you are using a version of Notepad++ older than v6.4.5, the rest of this answer still applies.

Natively

You can do this natively in Notepad++, but in order to replicate the behaviour of Firefox, you need to disable the document switcher and MRU behaviour.

Disable MRU functionality

1. Navigate to Settings > Preferences... > MISC..
   • Where it says Document Switcher (Ctrl+TAB) uncheck the first check box Enable.
   • Hit the Close button.

Create the Ctrl+PGUP/PGDN shortcuts

1. Navigate to Settings > Shortcut Mapper....
   • Make sure you are on the Main menu tab.
   • Scroll to the bottom and you should see in entries 192 Switch to previous document and 193 Switch to next document.
   • By default these should be mapped to Ctrl+Shift+Tab and Ctrl+Tab respectively.
   • Double click anywhere on the 192 line and change it to Ctrl+Page up.
   • Double click anywhere on the 193 line and change it to Ctrl+Page down.
   • Hit the Close button.

That's it!

Please note that you will no longer have access to the Ctrl+Tab/Shift+Tab MRU behaviour now. If, like me, you cannot live without this read on.

Another (better) option

Notepad++ defaults to using the back and forward buttons on a mouse to switch to the adjacent left and right tabs, so if you are a fan of AutoHotkey, you can use this little script:

#IfWinActive, ahk_class Notepad++
; Switch to the adjacent tab to the left
^PgUp::
    Send, {XButton1}
    Return
; Switch to the adjacent tab to the right
^PgDn::
    Send, {XButton2}
    Return

This won't interfere with other programs and enables to you have your cake and eat it! You can navigate left and right through adjacent the tabs using Ctrl+PgUp and Ctrl+PgDn and you can still switch to your last used tab using the built-in document switcher functionality using Ctrl+Tab and Ctrl+Shift+Tab - just like Firefox :)

Settings -> Preferences -> MISC, Document switcher (Ctrl-TAB). Uncheck the "Enable" checkbox. Documents will then be navigated to in the order they appear in the tabs.

You can also assign different keyboard shortcuts to next/previous document if you prefer.

Using AutoHotkey, if the mouse back and forward buttons are already mapped by the user for a different purpose, lukescammell's solution can be modified to use Browser_Back and Browser_Forward instead:

#IfWinActive, ahk_class Notepad++
; Switch to the adjacent tab to the left
^PgUp::
    Send, {Browser_Back}
    Return
; Switch to the adjacent tab to the right
^PgDn::
    Send, {Browser_Forward}
    Return

These are extra media buttons found on some multimedia keyboards for going back and forward in a Web browser.

Nowadays, this is the default behaviour, so if you are able to upgrade to the latest version of Notepad++, you should.

The new shortcuts 141 (Next Tab) and 142 (Previous Tab), which didn't exist until at least version 6.4.3, are now mapped to Ctrl+PgDn and Ctrl+PgUp.

This also circumvents the MRU dialog, so it's a double win.