I was under the impression that all ArcGIS package files could have their contents examined and potentially used by renaming them to *.zip and unzipping them.

This impression is supported for map package (*.mpk) files by @KHibma's answer to Opening MPK file without ArcGIS Desktop? and I thought I had used it succesfully on geoprocessing package (*.gpk) files in the past.

However, today I am unable to use a tool within a *.gpk which I think is because it was created using ArcGIS Desktop 10.5.x when I am using When I rename this *.gpk as *.zip and try to examine it in Windows Explorer I get:

Compressed (zipped) Folders Error

Windows cannot open the folder

The Compressed (zipped) Folder ....zip is invalid.

enter image description here

Is it possible to unzip a geoprocessing package (*.gpk) file to see whether it may contain some useful ArcPy code when that *.gpk cannot be unpacked to provide a usable toolbox?


1 Answer 1


Try .7z instead of .zip. the .*pk uses 7zip encoding and not zip.

Source - open a .*pk file in notepad++ or something and you will see the first characters are 7z. That is a 7zip header. Read more about the 7z file encoding here: http://cpansearch.perl.org/src/BJOERN/Compress-Deflate7-1.0/7zip/DOC/7zFormat.txt

Zip file headers start with a PK. Read more about zip encoding here: https://pkware.cachefly.net/webdocs/casestudies/APPNOTE.TXT

  • You may well be right. Unfortunately, I'm in a locked down environment and installing 7-zip to test may be challenging.
    – PolyGeo
    Nov 2, 2017 at 23:08
  • 1
    Use the version from portableapp.com. Nov 13, 2017 at 21:12

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