portable application

Most portable applications do not leave files or settings on the host computer or modify the existing system and its configuration. The application may not write to the Windows registry{{cite web | title = "What is a Portable App?" | publisher = PortableApps.com | access-date=2022-11-15 | url = https://portableapps.com/about/what_is_a_portable_app#guidelines |at = Guidelines}} or store its configuration files (such as an INI file) in the user's profile, but today, many portables do; many, however, still store their configuration files in the portable directory. Another possibility, since file paths will often differ on changing computers due to variation in drive letter assignments, is that portable applications may 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: 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 components or ActiveX, not only for the entire application.{{cite web|title=Portable Application Conversion Technology|url=http://sphinx-soft.com/Portable/|publisher=Sphinx Software|access-date=January 19, 2012|archive-url=https://web.archive.org/web/20100907213345/http://sphinx-soft.com/Portable/|archive-date=September 7, 2010}} 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 operating system (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.{{cite web|title=Portable Application Registry|url=http://ip.com/patapp/US20070136241|publisher=ip.com|access-date=January 19, 2012}} It eventually incorporated some of this technology, using the techniques mentioned above, via its Application Compatibility Database{{cite web|last=Ionescu|first=Alex|title=Secrets of the Application Compatilibity Database (SDB) – Part 1|url=http://www.alex-ionescu.com/?p=39|access-date=January 19, 2012}} using its Detours{{cite web|title=Detours|url=http://research.microsoft.com/en-us/projects/detours/|publisher=Microsoft Research|access-date=January 19, 2012}} code library, into Windows XP. It did not make any of this technology available via its system APIs.

{{See also|Autopackage|Zero Install}}

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 95/98/ME (and to some degree in Windows XP/2000, though not in Windows Vista or Windows 7)—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 environment variable to store settings (e.g. $HOME/.w3m for the w3m 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 option $ORIGIN which allows a relative library search path.{{cite web|url=http://blog.linuxgamepublishing.com/2009/02/08/our-new-way-to-meet-the-lgpl/|archive-url=https://web.archive.org/web/20090220234542/http://blog.linuxgamepublishing.com/2009/02/08/our-new-way-to-meet-the-lgpl/|archive-date=2009-02-20 |title= Our new way to meet the LGPL |date=2009-02-08|access-date= 2011-03-09 |first=Eskild |last= Hustvedt |quote= You can use a special keyword $ORIGIN to say 'relative to the actual location of the executable'. Suddenly we found we could use -rpath $ORIGIN/lib and it worked. The game was loading the correct libraries, and so was stable and portable, but was also now completely in the spirit of the LGPL as well as the letter!}}

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, AppImage, or CDE, but which gained only limited acceptance and support in the Linux community in the 2000s.{{cite web|url=http://www.gaslampgames.com/blog/2010/11/13/dear-linux-community-we-need-to-talk/|publisher=Gaslamp Games|title=Dear Linux Community: We Need To Talk. |date=2010-10-13 |first=Nicholas |last=Vining |access-date=2011-01-30 |quote=The Linux community, in their infinite wisdom, proceeds to flame the hell out of CDE. [...] "We should all just be using package management." Here is what I want to say, and let my words be carried down from the mountaintops, written on tiny stone tablets: Package management is not a universal panacea.}}{{cite web|archive-url=https://web.archive.org/web/20080331092730/http://www.linux.com/articles/60124 |url=http://www.linux.com/articles/60124|title=Autopackage struggling to gain acceptance |first=Bruce |last=Byfield |date=2007-02-12 |access-date=2012-01-21 |publisher=linux.com |archive-date=2008-03-31 |quote=If Hearn is correct, the real lesson of Autopackage is not how to improve software installation, but the difficulty -- perhaps the impossibility -- of large-scale changes in Linux architecture this late in its history. It's a sobering, disappointing conclusion to a project that once seemed so promising.}}{{cite web|title=AppImages|url=http://elementary-project.com/wiki/index.php?title=AppImages|publisher=Elementary Project |access-date=January 19, 2012|archive-url=https://web.archive.org/web/20101213215610/http://elementary-project.com/wiki/index.php?title=AppImages|archive-date=December 13, 2010}} Around 2015 the idea of portable and distro independent packing for the Linux ecosystem got more traction when Linus Torvalds discussed this topic on the DebConf 2014 and endorsed later AppImage for his dive log application Subsurface.{{cite web|url=http://meetings-archive.debian.net/pub/debian-meetings/2014/debconf14/webm/QA_with_Linus_Torvalds.webm |title=Q&A with Linus Torvalds |author=Linus Torvalds |author-link=Linus Torvalds |date=2014-08-29 |publisher=debian.net |work=DebConf 2014 Portland |access-date=2016-05-14 |format=video |at=6:28 |quote=I have seen this first hand with the other project I'm involved with, which is my dive log app. We make binaries for Windows and OSX, we basically don't make binaries for Linux. Why? Because making binaries for Linux desktop applications is a major fucking pain in the ass.}}{{cite web|url=https://plus.google.com/+LinusTorvalds/posts/WyrATKUnmrS|title=This is just very cool.|last=Torvalds|first=Linus|author-link=Linus Torvalds|publisher=Google+|quote=I finally got around to play with the "AppImage" version of +Subsurface, and it really does seem to "just work".}}{{cite web|url=https://plus.google.com/+LinusTorvalds/posts/WyrATKUnmrS|title=This is just very cool. |last=Hohndel |first=Dirk|publisher=Google+|quote=I, as the app maintainer, don't want my app bundled in a distribution anymore. Way to much pain for absolutely zero gain. Whenever I get a bug report my first question is "oh, which version of which distribution? which version of which library? What set of insane patches were applied to those libraries?". No, Windows and Mac get this right. I control the libraries my app runs against. [...] With an AppImage I can give them just that. Something that runs on their computer.|date=2015-11-25}} For instance, MuseScore and Krita followed in 2016 and started to use AppImage builds for software deployment.{{cite web|last1=Weiss|first1=Isaac|title=MuseScore 2.0.3 is released|url=https://musescore.org/en/node/104676|website=MuseScore.org|publisher=MuseScore|access-date=2016-04-05|archive-url=https://web.archive.org/web/20160423053503/https://musescore.org/en/node/104676|archive-date=2016-04-23}}{{cite web|title=Krita 3.0 Released|url=https://krita.org/item/krita-3-0-released/ |website=Krita.org |publisher=Krita |date=2016-05-31}} RedHat released in 2016 the Flatpak system, which is a successor of Alexander Larsson's glick project which was inspired by klik (now called AppImage).[https://blogs.gnome.org/alexl/2007/08/07/experiments-with-runtime-less-app-bundles/ Experiments with run-timeless app bundles] by Alex Larsson (2007) Similarly, Canonical released in 2016 Snap packages for Ubuntu and many other Linux distros.

Many Mac applications that can be installed by drag-and-drop are inherently portable as Mac application bundles.{{cite web | title = Distributing Your Application | publisher = developer.apple.com | access-date=2017-05-23 | url = https://developer.apple.com/library/content/documentation/Porting/Conceptual/PortingUnix/distributing/distibuting.html}} Examples include Mozilla Firefox, Skype and Google Chrome 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.{{cite web | title = Distribution XML Reference | publisher = developer.apple.com | access-date=2017-05-23 | url = https://developer.apple.com/library/content/documentation/DeveloperTools/Reference/DistributionDefinitionRef/Chapters/Distribution_XML_Ref.html#//apple_ref/doc/uid/TP40005370-CH100-SW35}} Such an installation is performed as the user.

• Load drive
• List of portable software
• WinPenPack
• Portable application creators
• PortableApps.com
• U3
• Application virtualization
• Turbo (software)
• VMware ThinApp
• Live USB
• Ceedo
• Portable-VirtualBox
• Windows To Go
• Data portability
• Interoperability

{{Reflist}}