What does the -oX flag do in an Nmap scan?

An Xmas scan is invoked with the -sX flag (scan type), not -oX; the lowercase 'o' prefix in Nmap flags designates output format, not scan type.

There is no 'eXpress scan' mode in Nmap; this is a fabricated option that does not correspond to any valid Nmap flag.

Nmap does not have a truncated screen output format; the -oX flag writes to a file, not to the screen, and produces full XML-structured output rather than a shortened view.

The -oX <filename> flag in Nmap outputs results in structured XML format to the named file, allowing integration with other security tools, vulnerability management platforms, and automated parsers. It is one of three major output format flags in Nmap (-oN for normal, -oG for grepable, -oX for XML). The -oA flag can be used to output all three formats simultaneously.