Hi, This is something I ask myself. I looked over internet but nothing explicit. How to know if a application is truly a portable Application ?

Does this mean when I execute the application:
- no entries in registry a created ?
- no folder in the %AppData% folder for the application setting are created ?

Is there also a diference betwen a zip package file downloaded and a file downloaded from a Portable application website like example Keepass

From Keepass website
Portable KeePass 1.16 (ZIP Package)
Download this ZIP package and unpack it to your favorite location (USB stick, ...). KeePass runs without any additional installation and won't store any settings outside the application directory

and this one : http://portableapps.com/apps/utilities/keepass_portable

To make sure it is truly portable, you would have to take a reg shot. If there are any changes, then it isnt portable. In some cases, if you are running programs (MSN/Xfire/Steam), there will be reg changes.

Any registry changes made are deleted when the program exits. The same goes for any files or folders.

ok then i'll do some test to check that.

For truly portable applications nothing can be written to the registry or outside the application folder.
However, there are some apps that do use the registry for some things and then delete their own entries, or ones that use a settings file in AppData and nothing more, which make them "almost portable".

You can use Sysinternals Process Monitor to see if something is being written to the registry. I have found it much better than using registry snapshots because nowadays many programs are writing things there and it gets confusing at times to know for sure which app wrote what.

Thank elajua