pgpdump is a PGP packet visualizer written by Kazu Yamamoto. The available options are listed on the manual page, the source code can be found in the git repository.
To use this web interface, upload the OpenPGP/PGP datafile to analyze, either in binary format or ASCII armored, with a size not exceeding 2MB. The file is passed to pgpdump version 0.31, copyright (C) 1998-2016 Kazu Yamamoto. Your data is deleted immediately after processing. However, do not upload sensitive material like your secret key.