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Mirror sites or mirrors are replicas of other
website A website (also written as a web site) is any web page whose content is identified by a common domain name and is published on at least one web server. Websites are typically dedicated to a particular topic or purpose, such as news, educatio ...
s. The concept of mirroring applies to network services accessible through any protocol, such as
HTTP HTTP (Hypertext Transfer Protocol) is an application layer protocol in the Internet protocol suite model for distributed, collaborative, hypermedia information systems. HTTP is the foundation of data communication for the World Wide Web, wher ...
or
FTP The File Transfer Protocol (FTP) is a standard communication protocol used for the transfer of computer files from a server to a client on a computer network. FTP is built on a client–server model architecture using separate control and dat ...
. Such sites have different
URL A uniform resource locator (URL), colloquially known as an address on the Web, is a reference to a resource that specifies its location on a computer network and a mechanism for retrieving it. A URL is a specific type of Uniform Resource Identi ...
s than the original site, but host identical or near-identical content. Mirror sites are often located in a different
geographic region In geography, regions, otherwise referred to as areas, zones, lands or territories, are portions of the Earth's surface that are broadly divided by physical characteristics (physical geography), human impact characteristics (human geography), and ...
than the original, or upstream site. The purpose of mirrors is to reduce
network traffic Network traffic or data traffic is the amount of data moving across a network at a given point of time. Network data in computer networks is mostly encapsulated in network packets, which provide the load in the network. Network traffic is the main ...
, improve access speed, ensure availability of the original site for technical or political reasons, or provide a real-time backup of the original site. Mirror sites are particularly important in
developing countries A developing country is a sovereign state with a less-developed Secondary sector of the economy, industrial base and a lower Human Development Index (HDI) relative to developed countries. However, this definition is not universally agreed upon. ...
, where internet access may be slower or less reliable. Mirror sites were heavily used on the early internet, when most users accessed through dialup and the
Internet backbone The Internet backbone is the principal data routes between large, strategically interconnected computer networks and core routers of the Internet. These data routes are hosted by commercial, government, academic and other high-capacity network ...
had much lower bandwidth than today, making a geographically-localized mirror network a worthwhile benefit. Download archives such as Info-Mac,
Tucows Tucows Inc. is an American-Canadian publicly traded Internet services and telecommunications company headquartered in Toronto, Ontario, Canada, and incorporated in Pennsylvania, United States. The company is composed of three independent business ...
and
CPAN The Comprehensive Perl Archive Network (CPAN) is a software repository of over 220,000 software modules and accompanying documentation for 45,500 distributions, written in the Perl programming language by over 14,500 contributors. ''CPAN'' can de ...
maintained worldwide networks mirroring their content accessible over
HTTP HTTP (Hypertext Transfer Protocol) is an application layer protocol in the Internet protocol suite model for distributed, collaborative, hypermedia information systems. HTTP is the foundation of data communication for the World Wide Web, wher ...
or anonymous FTP. Some of these networks, such as Info-Mac or Tucows are no longer active or have removed their mirrored download sections, but some like CPAN or the
Debian Debian () is a free and open-source software, free and open source Linux distribution, developed by the Debian Project, which was established by Ian Murdock in August 1993. Debian is one of the oldest operating systems based on the Linux kerne ...
package mirrors are still active in 2023. Debian removed FTP access to its mirrors in 2017 because of declining use and the relative stagnation of the FTP protocol, mentioning FTP servers' lack of support for techniques such as caching and load balancing that are available to HTTP. Modern mirrors support
HTTPS Hypertext Transfer Protocol Secure (HTTPS) is an extension of the Hypertext Transfer Protocol (HTTP). It uses encryption for secure communication over a computer network, and is widely used on the Internet. In HTTPS, the communication protoc ...
and IPv6 along with IPv4. On occasion, some mirrors may choose not to replicate the entire contents of the upstream server because of technical constraints, or selecting only a subset relevant to their purpose, such as software written in a particular
programming language A programming language is a system of notation for writing computer programs. Programming languages are described in terms of their Syntax (programming languages), syntax (form) and semantics (computer science), semantics (meaning), usually def ...
, runnable on a single computer platform, or written by one author. These sites are called partial mirrors or secondary mirrors.


Examples

Notable websites with mirrors include
Project Gutenberg Project Gutenberg (PG) is a volunteer effort to digitize and archive cultural works, as well as to "encourage the creation and distribution of eBooks." It was founded in 1971 by American writer Michael S. Hart and is the oldest digital li ...
, KickassTorrents,
The Pirate Bay The Pirate Bay, commonly abbreviated as TPB, is a free searchable online index of Film, movies, music, video games, Pornographic film, pornography and software. Founded in 2003 by Swedish think tank , The Pirate Bay facilitates the connection ...
,
WikiLeaks WikiLeaks () is a non-profit media organisation and publisher of leaked documents. It is funded by donations and media partnerships. It has published classified documents and other media provided by anonymous sources. It was founded in 2006 by ...
, the website of the Environmental Protection Agency, and
Wikipedia Wikipedia is a free content, free Online content, online encyclopedia that is written and maintained by a community of volunteers, known as Wikipedians, through open collaboration and the wiki software MediaWiki. Founded by Jimmy Wales and La ...
. Some notable partial mirrors include
free and open-source software Free and open-source software (FOSS) is software available under a license that grants users the right to use, modify, and distribute the software modified or not to everyone free of charge. FOSS is an inclusive umbrella term encompassing free ...
projects such as GNU, in particular
Linux Linux ( ) is a family of open source Unix-like operating systems based on the Linux kernel, an kernel (operating system), operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically package manager, pac ...
distributions
CentOS CentOS (, from Community Enterprise Operating System; also known as CentOS Linux) is a discontinued Linux distribution that provided a free and open-source community-supported computing platform, functionally compatible with its upstream (softw ...
,
Debian Debian () is a free and open-source software, free and open source Linux distribution, developed by the Debian Project, which was established by Ian Murdock in August 1993. Debian is one of the oldest operating systems based on the Linux kerne ...
, Fedora, and
Ubuntu Ubuntu ( ) is a Linux distribution based on Debian and composed primarily of free and open-source software. Developed by the British company Canonical (company), Canonical and a community of contributors under a Meritocracy, meritocratic gover ...
; such projects provide mirrors of the download sites (since those are expected to have high server load). Many
open source Open source is source code that is made freely available for possible modification and redistribution. Products include permission to use and view the source code, design documents, or content of the product. The open source model is a decentrali ...
application providers such as VideoLAN use mirrors to distribute
VLC Media Player VLC media player (previously the VideoLAN Client) is a free and open-source software, free and open-source, software portability, portable, cross-platform media player software and streaming media Server (computing), server developed by the Vide ...
, and The Document Foundation uses mirrors to distribute
LibreOffice LibreOffice () is a free and open-source office productivity software suite developed by The Document Foundation (TDF). It was created in 2010 as a fork of OpenOffice.org, itself a successor to StarOffice. The suite includes applications ...
. It was once common for tech companies such as
Microsoft Microsoft Corporation is an American multinational corporation and technology company, technology conglomerate headquartered in Redmond, Washington. Founded in 1975, the company became influential in the History of personal computers#The ear ...
,
Hewlett-Packard The Hewlett-Packard Company, commonly shortened to Hewlett-Packard ( ) or HP, was an American multinational information technology company. It was founded by Bill Hewlett and David Packard in 1939 in a one-car garage in Palo Alto, California ...
or
Apple An apple is a round, edible fruit produced by an apple tree (''Malus'' spp.). Fruit trees of the orchard or domestic apple (''Malus domestica''), the most widely grown in the genus, are agriculture, cultivated worldwide. The tree originated ...
to maintain a network of mirrors accessible over HTTP or anonymous FTP, hosting
software updates A patch is data that is intended to be used to modify an existing software resource such as a program or a file, often to fix bugs and security vulnerabilities. A patch may be created to improve functionality, usability, or performance. A pa ...
, sample code and various freely-downloadable
utilities A public utility company (usually just utility) is an organization that maintains the infrastructure for a public service (often also providing a service using that infrastructure). Public utilities are subject to forms of public control and r ...
. Much of these sites were shut down in the first decades of the 21st century, with Apple shutting down its FTP services in 2012 and Microsoft stopping updates in 2010. Today, the contents of a number of these mirror sites are archived at The FTP Site Boneyard. Occasionally, some people will use
web scraping Web scraping, web harvesting, or web data extraction is data scraping used for data extraction, extracting data from websites. Web scraping software may directly access the World Wide Web using the Hypertext Transfer Protocol or a web browser. W ...
software to produce static dumps of existing sites, such as the BBC's ''Top Gear'' and RedFlagDeals.


See also

*
InterPlanetary File System The InterPlanetary File System (IPFS) is a protocol, hypermedia and file sharing peer-to-peer network for sharing data using a distributed hash table to store provider information. By using content addressing, IPFS uniquely identifies each fi ...
– makes mirror sites redundant *
Content delivery network A content delivery network (CDN) or content distribution network is a geographically distributed network of proxy servers and their data centers. The goal is to provide high availability and performance ("speed") by distributing the service spat ...
*
cURL cURL (pronounced like "curl", ) is a free and open source computer program for transferring data to and from Internet servers. It can download a URL from a web server over HTTP, and supports a variety of other network protocols, URI scheme ...
* Cyber resilience *
Dark web The dark web is the World Wide Web content that exists on darknets ( overlay networks) that use the Internet but require specific software, configurations, or authorization to access. Through the dark web, private computer networks can communica ...
*
DDoS In computing, a denial-of-service attack (DoS attack) is a cyberattack in which the perpetrator seeks to make a machine or network resource unavailable to its intended users by temporarily or indefinitely disrupting services of a host co ...
*
Downtime In computing and telecommunications, downtime (also (system) outage or (system) drought colloquially) is a period when a system is unavailable. The unavailability is the proportion of a time-span that a system is unavailable or offline. This is ...
* HTTrack *
IRC network IRC (Internet Relay Chat) is a text-based chat system for instant messaging. IRC is designed for Many-to-many, group communication in discussion forums, called ''#Channels, channels'', but also allows one-on-one communication via instant mess ...
*
Mesh networking A mesh network is a local area network network topology, topology in which the infrastructure Node (networking), nodes (i.e. bridges, switches, and other infrastructure devices) connect directly, dynamically and non-hierarchically to as many othe ...
*
Peer-to-peer Peer-to-peer (P2P) computing or networking is a distributed application architecture that partitions tasks or workloads between peers. Peers are equally privileged, equipotent participants in the network, forming a peer-to-peer network of Node ...
*
Replication (computing) Replication in computing refers to maintaining multiple copies of data, processes, or resources to ensure consistency across redundant components. This fundamental technique spans databases, file systems, and distributed systems, serving to impro ...
*
Web archiving Web archiving is the process of collecting, preserving, and providing access to material from the World Wide Web. The aim is to ensure that information is preserved in an archival format for research and the public. Web archivists typically ...
*
Website monitoring Website monitoring is the process of testing and verifying that end-users can interact with a website or web application as expected. Website monitoring are often used by businesses to ensure website uptime, performance, and functionality is as ex ...
*
Wget GNU Wget (or just Wget, formerly Geturl, also written as its package name, wget) is a computer program that retrieves content from web servers. It is part of the GNU Project. Its name derives from "World Wide Web" and " ''get''", a HTTP reque ...
* Wikipedia:Mirrors and forks


References


External links

{{Websites template Websites Data synchronization Disaster preparedness Web 1.0