Zero Install is a means of distributing and packaging software for multiple operating systems (Linux and Unix-like, OS X, and Windows). Many distributions offer it as an additional non-default component.
Rather than the normal method of downloading a software package, extracting it, and installing it before it can be used (with the accompanying use of destructive updates and privilege escalation), packages distributed using Zero Install need only be run. The first time software is accessed, it is downloaded from the Internet and cached; subsequently, software is accessed from the cache. Programs are accessed by the fully qualified name of their URL; for example one would not run "myeditor textfile.txt", but "http://www.example.org/edit textfile.txt". Inside the cache, each application unpacks to its own directory, as in Application Directory systems.
The system is implemented as a Python program, called the Injector (a reference to Dependency injection). The system is intended to be used alongside a distribution's native package manager.
The main advantage of Zero Install over more popular packaging systems is that no root password is needed to install software; packages can be installed in system locations writable by that user instead of requiring administrator access. Thus, package installation affects only the user installing it, which makes it possible for all users to be able to install and run new software.
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