A portable application (portable app), sometimes also called standalone, is a program designed to run on a compatible computer without being installed leaving the computer’s configuration information intact. This type of application can be stored on any storage facility, including internal mass storage, a file share, cloud storage or external storage such as USB drives and floppy disks – storing its program files and any configuration information and data on the storage medium alone. If no configuration information is required a portable program can be run from read-only storage such as CD-ROMs and DVD-ROMs. Such applications are commonly used on restricted machines due to the nature in which they do not interact or modify the system. They are considered safe since they run the same executable code and thus neither add nor retract any functionality of their installable counterparts. Some applications are available in both installable and portable versions.
Some applications which are not portable by default support optional portability through other mechanisms, the most common being command-line arguments. Examples might include /portable to simply instruct the program to behave as a portable program, or –cfg=/path/inifile to specify the configuration file location.
Like any application, portable applications must be compatible with the computer system hardware and operating system.
Depending on the operating system, portability is more or less complex to implement; to operating systems such as AmigaOS, all applications are by definition portable. Portable apps are distinct from software portability, source code written to be compilable into different executable programs for different computing platforms.