Assigning custom extensions to a language's syntax highlighting in Notepad++

In the current version of Notepad++ opening .sql files results in Notepad applying SQL syntax highlighting to it. I'd like Notepad++ to do the same for other extensions as well, is there some setting where I can define this?

When you open a file in notepad++ it will attempt to load syntax highlighting for the contents based on file extension.

If you use a custom extension for one of the existing languages you can add the custom extension in Settings -> Style Configurator. Select language and add the extension in the "User extension" edit box. To add multiple extensions separate them using Space.

You then need to re-open your file to see the syntax highlighting applied.

You can also change syntax highlighting style by selecting a different language from the language menu.

Find the langs.xml file (usually under C:\Users[username]\AppData\Roaming\Notepad++), open it with Notepad++, find the line that begins with <Language name="sql" ext="sql" and add the extensions you want in the ext field, separating them with a space.

To do this for a user-defined language, look instead for userDefineLang.xml and edit ext="".

If you installed notepad++ in "portable"-mode, then the langs.xml and userDefineLangs.xml will be directly in the folder where notepad++ is located.