This package looks for pdfTeX in pdf mode and implements and sets the switch \ifpdf. The detection is based on the value of \pdfoutput (which the package will not change). The package works with plain or LaTeX formats. To use it with LaTeX simply \usepackage{ifpdf}. Then use \ifpdf ... \else ... \fi.

The author is Heiko Oberdiek. The package is Copyright © 2001,2005-2011 Heiko Oberdiek.