Below are steps to Auto-Format/Indent XML in Notepad++
Step 1: Open your XML file with Notepad++
Step 2: Navigate to the “Plugins” menu option, then choose “Plugins Admin” from the dropdown option.
Step 3: Search “XML Tools," then check-mark it, and click on Install.
Step 4: Confirm the installation
Step 5: Then restart Notepad++, again go back to the “Plugins” menu, and select XML Tools.
Step 6: Click on Pretty Print to auto-format the XML file.
For HTML, the process is the same, but you can use some HTML-specific beautifier or plugin like the XML tool Plugin, TextFX plugin, or HTMLTidy tool for better formatting.