Mirror sites or mirrors are replicas of other
websites. The concept of mirroring applies to network services accessible through any protocol, such as
HTTP or
FTP. Such sites have different
URLs than the original site, but host identical or near-identical content.[1] Mirror sites are often located in a different
geographic region than the original, or upstream site. The purpose of mirrors is to reduce
network traffic, improve
access speed, ensure availability of the original site for technical[2] or political reasons,[3] or provide a real-time backup of the original site.[4][5][6] Mirror sites are particularly important in
developing countries, where internet access may be slower or less reliable.[7]
Mirror sites were heavily used on the early internet, when most users accessed through
dialup and the
Internet backbone had much lower bandwidth than today, making a geographically-localized mirror network a worthwhile benefit. Download archives such as
Info-Mac,
Tucows and
CPAN maintained worldwide networks mirroring their content accessible over
HTTP 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 Some of these networks, such as Info-Mac or Tucows are no longer active or have removed their mirrored download sections, but some like CPAN or the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 package mirrors are still active in 2023.[8] 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.[9] Modern mirrors support
HTTPS and IPv6 along with IPv4.[10]
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, runnable on a single
computer platform, or written by one author. These sites are called partial mirrors or secondary mirrors.[11]
It was once common for tech companies such as
Microsoft,
Hewlett-Packard or
Apple to maintain a network of mirrors accessible over HTTP or anonymous FTP, hosting
software updates,
sample code and various freely-downloadable
utilities. 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.[36][37] Today, the contents of a number of these mirror sites are archived at The FTP Site Boneyard.[38] Occasionally, some people will use
web scraping software to produce
static dumps of existing sites, such as the BBC's Top Gear and RedFlagDeals.
^"Debian worldwide mirror sites".
Archived from the original on 6 September 2017. Retrieved 27 August 2017. Using a nearby server will probably speed up your download, and also reduce the load on our central servers and on the Internet as a whole.
^"Impending Trump has Internet Archive mirror to Canada". 29 November 2016.
Archived from the original on 11 December 2019. Retrieved 11 December 2019. The Internet Archive has several mirrors up right now, and Canada is set to be its next. This move is taking place specifically because of the new presidential elect Trump here in the United States.
^Sekikawa, A.; Sa, E. R.; Acosta, B.; Aaron, D. J.; Laporte, R. E. (2000).
"Internet mirror sites - The Lancet". Lancet. 355 (9219): 2000.
doi:
10.1016/s0140-6736(05)72944-5.
PMID10859070.
S2CID32218172.
Archived from the original on 6 October 2022. Retrieved 11 December 2019. We all become frustrated when web pages take minutes to unfold. This can increase the gap between infrastructure haves and have-nots. Downloading time is important for other reasons; users connecting to the internet via telephone line in many countries are charged per minute and slow downloading itself may make users lose interest.
^Nestor, Marius (26 April 2017).
"Debian Project to Shut Down Its Public FTP Services, Developers Are Not Affected". Softpedia.
Archived from the original on 8 February 2024. The decision to close the Debian FTP services for users was made because the FTP servers in their current state lack support for acceleration or caching, and they aren't quite used lately due to the fact that the Debian Installer no longer provides an FTP option for accessing mirrors since more than ten years ago... FTP as a protocol appears to no longer be efficient, requiring adding strange workarounds to firewalls and load-balancing daemons.
^"CSpace Hostings Public Mirror".
Archived from the original on 21 January 2021. Retrieved 21 January 2021. This page and mirror are available over IPv4 and IPv6 and accessible over HTTP, HTTPS and Rsync
^"Debian worldwide mirror sites".
Archived from the original on 6 September 2017. Retrieved 27 August 2017. A secondary mirror site may have restrictions on what they mirror
^"Project Gutenberg, nonprofit organization".
Archived from the original on 13 July 2021. Retrieved 11 December 2019. In addition, dozens of "mirror" Web sites were created around the world, where the e-books were also stored and available for downloading.