A portable application (portable app), sometimes also called standalone, is a

program Program, programme, programmer, or programming may refer to: Business and management * Program management, the process of managing several related projects * Time management * Program, a part of planning Arts and entertainment Audio * Progra ...

designed to read and write its configuration settings into an accessible folder in the computer, usually in the folder where the portable application can be found. This makes it easier to transfer the program with the user's preferences and data between different computers. A program that doesn't have any configuration options can also be a portable application. Portable applications can be stored on any

data storage device Data storage is the recording (storing) of information (data) in a storage medium. Handwriting, phonographic recording, magnetic tape, and optical discs are all examples of storage media. Biological molecules such as RNA and DNA are conside ...

, including internal

mass storage In computing, mass storage refers to the storage of large amounts of data in a persisting and machine-readable fashion. In general, the term is used as large in relation to contemporaneous hard disk drives, but it has been used large in relati ...

, a file share,

cloud storage Cloud storage is a model of computer data storage in which the digital data is stored in logical pools, said to be on "the cloud". The physical storage spans multiple servers (sometimes in multiple locations), and the physical environment is t ...

or external storage such as USB drives and

floppy disk A floppy disk or floppy diskette (casually referred to as a floppy, or a diskette) is an obsolescent type of disk storage composed of a thin and flexible disk of a magnetic storage medium in a square or nearly square plastic enclosure lined w ...

s—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-ROM A CD-ROM (, compact disc read-only memory) is a type of read-only memory consisting of a pre-pressed optical compact disc that contains data. Computers can read—but not write or erase—CD-ROMs. Some CDs, called enhanced CDs, hold both comput ...

s and

DVD-ROM The DVD (common abbreviation for Digital Video Disc or Digital Versatile Disc) is a digital optical disc data storage format. It was invented and developed in 1995 and first released on November 1, 1996, in Japan. The medium can store any ki ...

s. Some applications are available in both installable and portable versions. Some applications which are not portable by default do 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 An operating system (OS) is system software that manages computer hardware, software resources, and provides common services for computer programs. Time-sharing operating systems schedule tasks for efficient use of the system and may also in ...

. Depending on the operating system, ''portability'' is more or less complex to implement; to operating systems such as

AmigaOS AmigaOS is a family of proprietary native operating systems of the Amiga and AmigaOne personal computers. It was developed first by Commodore International and introduced with the launch of the first Amiga, the Amiga 1000, in 1985. Early version ...

, all applications are by definition portable.

Portable Windows applications

A portable application does not leave its files or settings on the host computer or modify the existing system and its configuration. The application does not write to the

Windows registry The Windows Registry is a hierarchical database that stores low-level settings for the Microsoft Windows operating system and for applications that opt to use the registry. The kernel, device drivers, services, Security Accounts Manager, and use ...

nor stores its configuration files (such as an INI file) in the user's

profile Profile or profiles may refer to: Art, entertainment and media Music * ''Profile'' (Jan Akkerman album), 1973 * ''Profile'' (Githead album), 2005 * ''Profile'' (Pat Donohue album), 2005 * ''Profile'' (Duke Pearson album), 1959 * '' ''Profi ...

; instead, it stores its configuration files in the portable directory. Another requirement, since file paths will often differ on changing computers due to variation in

drive letter assignment In computer data storage, drive letter assignment is the process of assigning alphabetical identifiers to volumes. Unlike the concept of UNIX mount points, where volumes are named and located arbitrarily in a single hierarchical namespace, driv ...

s, is the need for applications to store them in a ''relative'' format. While some applications have options to support this behavior, many programs are not designed to do this. A common technique for such programs is the use of a launcher program to copy necessary settings and files to the host computer when the application starts and move them back to the application's directory when it closes. An alternative strategy for achieving application portability within Windows, without requiring application source code changes, is

application virtualization Application virtualization is a software technology that encapsulates computer programs from the underlying operating system on which they are executed. A fully virtualized application is not installed in the traditional sense, although it is stil ...

: An application is "sequenced" or "packaged" against a runtime layer that transparently intercepts its file system and registry calls, then redirects these to other persistent storage without the application's knowledge. This approach leaves the application itself unchanged, yet portable. The same approach is used for individual application components: run-time libraries,

COM Com or COM may refer to: Computing * COM (hardware interface), a serial port interface on IBM PC-compatible computers * COM file, or .com file, short for "command", a file extension for an executable file in MS-DOS * .com, an Internet top-level d ...

components or

ActiveX ActiveX is a deprecated software framework created by Microsoft that adapts its earlier Component Object Model (COM) and Object Linking and Embedding (OLE) technologies for content downloaded from a network, particularly from the World Wide Web. ...

, not only for the entire application. As a result, when individual components are ported in such manner they are able to be: integrated into original portable applications, repeatedly instantiated (virtually installed) with different configurations/settings on the same

(OS) without mutual conflicts. As the ported components do not affect the OS-protected related entities (registry and files), the components will not require administrative privileges for installation and management. Microsoft saw the need for an application-specific registry for its Windows operating system as far back as 2005. It eventually incorporated some of this technology, using the techniques mentioned above, via its Application Compatibility Database using its Detours code library, into Windows XP. It did not make any of this technology available via its system

API An application programming interface (API) is a way for two or more computer programs to communicate with each other. It is a type of software interface, offering a service to other pieces of software. A document or standard that describes how ...

Portability on Unix-like systems

Programs written with a Unix-like base in mind often do not make any assumptions. Whereas many Windows programs assume the user is an administrator—something very prevalent in the days of

Windows 95 Windows 95 is a consumer-oriented operating system developed by Microsoft as part of its Windows 9x family of operating systems. The first operating system in the 9x family, it is the successor to Windows 3.1x, and was released to manufacturin ...

/ 98/ ME (and to some degree in

Windows XP Windows XP is a major release of Microsoft's Windows NT operating system. It was released to manufacturing on August 24, 2001, and later to retail on October 25, 2001. It is a direct upgrade to its predecessors, Windows 2000 for high-end and ...

2000 File:2000 Events Collage.png, From left, clockwise: Protests against Bush v. Gore after the 2000 United States presidential election; Heads of state meet for the Millennium Summit; The International Space Station in its infant form as seen from ...

, though not in

Windows Vista Windows Vista is a major release of the Windows NT operating system developed by Microsoft. It was the direct successor to Windows XP, which was released five years before, at the time being the longest time span between successive releases of ...

Windows 7 Windows 7 is a major release of the Windows NT operating system developed by Microsoft. It was released to manufacturing on July 22, 2009, and became generally available on October 22, 2009. It is the successor to Windows Vista, released nearly ...

)—such would quickly result in "Permission denied" errors in Unix-like environments since users will be in an unprivileged state much more often. Programs are therefore generally designed to use the

HOME 









A home, or domicile, is a space used as a permanent or semi-permanent residence for one or many humans, and sometimes various companion animals. It is a fully or semi sheltered space and can have both interior and exterior aspects to it. H ...

environment variable An environment variable is a dynamic-named value that can affect the way running processes will behave on a computer. They are part of the environment in which a process runs. For example, a running process can query the value of the TEMP env ...

to store settings (e.g. ''$HOME''/.w3m for the

w3m w3m is a free software/ open source text-based web browser and terminal pager. It has support for tables, frames, SSL connections, color, and inline images on suitable terminals. Generally, it renders pages in a form as true to their origi ...

browser). The dynamic linker provides an environment variable LD_LIBRARY_PATH that programs can use to load libraries from non-standard directories. Assuming /mnt contains the portable programs and configuration, a command line may look like: HOME=/mnt/home/user LD_LIBRARY_PATH=/mnt/usr/lib /mnt/usr/bin/w3m www.example.com A Linux application without need for a user-interaction (e.g. adapting a script or environment variable) on varying directory paths can be achieved with the GCC

Linker Linker or linkers may refer to: Computing * Linker (computing), a computer program that takes one or more object files generated by a compiler or generated by an assembler and links them with libraries, generating an executable program or shar ...

option $ORIGIN which allows a relative library search path. Not all programs honor this—some completely ignore $HOME and instead do a user look-up in /etc/passwd to find the home directory, therefore thwarting portability. There are also cross-distro package formats that do not require admin rights to run, like

Autopackage Autopackage is a free software, free computer package management system aimed at making it simple to create a package that can be installed on all Linux distributions, created by Mike Hearn around 2002. In August 2010, Listaller and Autopackage ...

klik KLIK (1240 AM), branded as Newstalk 1240, is a radio station broadcasting a News Talk Information format. Licensed to Jefferson City, Missouri, United States, the station serves the Columbia, Missouri area. The station is currently owned by Cum ...

(now called AppImage), or CDE, but which gained only limited acceptance and support in the Linux community in the 2000s. Around 2015 the idea of portable and distro independent packing for the Linux ecosystem got more traction when

Linus Torvalds Linus Benedict Torvalds ( , ; born 28 December 1969) is a Finnish software engineer who is the creator and, historically, the lead developer of the Linux kernel, used by Linux distributions and other operating systems such as Android. He also c ...

discussed this topic on the

DebConf is a software utility for performing system-wide configuration tasks on Unix-like operating systems. It is developed for the Debian Linux distribution, and is closely integrated with Debian's package management system, dpkg. When packages are ...

2014 and endorsed later

AppImage AppImage is a format for distributing portable software on Linux without needing superuser permissions to install the application. It tries also to allow Linux distribution-agnostic binary software deployment for application developers, als ...

for his

dive log A dive log is a record of the diving history of an underwater diver. The log may either be in a book, locally hosted software, or web based. The log serves purposes both related to safety and personal records. Information in a log may contain the ...

application Subsurface. For instance, MuseScore and

Krita Krita ( ) is a free and open-source raster graphics editor designed primarily for digital art and 2D animation. The software runs on Windows, macOS, Linux Linux ( or ) is a family of open-source Unix-like operating systems based on th ...

followed in 2016 and started to use AppImage builds for software deployment. RedHat released in 2016 the

Flatpak Flatpak, formerly known as xdg-app, is a utility for software deployment and package management for Linux. It is advertised as offering a sandbox environment in which users can run application software in isolation from the rest of the system. ...

system, which is a successor of Alexander Larsson's ''glick'' project which was inspired by klik (now AppImage). Similarly,

Canonical The adjective canonical is applied in many contexts to mean "according to the canon" the standard, rule or primary source that is accepted as authoritative for the body of knowledge or literature in that context. In mathematics, "canonical example ...

released in 2016 Snap packages for

Ubuntu Ubuntu ( ) is a Linux distribution based on Debian and composed mostly of free and open-source software. Ubuntu is officially released in three editions: ''Desktop'', ''Server'', and ''Core'' for Internet of things devices and robots. All the ...

and many other Linux distros. Many Mac applications that can be installed by drag-and-drop are inherently portable as Mac application bundles. Examples include

Mozilla Firefox Mozilla Firefox, or simply Firefox, is a free and open-source web browser developed by the Mozilla Foundation and its subsidiary, the Mozilla Corporation. It uses the Gecko rendering engine to display web pages, which implements current and a ...

Skype Skype () is a proprietary telecommunications application operated by Skype Technologies, a division of Microsoft, best known for VoIP-based videotelephony, videoconferencing and voice calls. It also has instant messaging, file transfer, deb ...

and

Google Chrome Google Chrome is a cross-platform web browser developed by Google. It was first released in 2008 for Microsoft Windows, built with free software components from Apple WebKit and Mozilla Firefox. Versions were later released for Linux, macOS ...

which do not require admin access and do not need to be placed into a central, restricted area. Applications placed into /Users/username/Applications (~/Applications) are registered with macOS LaunchServices in the same way as applications placed into the main /Applications folder. For example, right-clicking a file in Finder and then selecting "Open With..." will show applications available from both /Applications and ~/Applications. Developers can create Mac product installers which allow the user to perform a home directory install, labelled "Install for me only" in the Installer user interface. Such an installation is performed as the user.

References

{{Reflist

Portable Windows applications

Portability on Unix-like systems

See also

References