Mirror sites ormirrors are replicas of otherwebsites. The concept of mirroring applies to network services accessible through any protocol, such asHTTP orFTP. Such sites have differentURLs than the original site, but host identical or near-identical content.[1] Mirror sites are often located in a differentgeographic region than the original, or upstream site. The purpose of mirrors is to reducenetwork traffic, improveaccess 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 indeveloping countries, where internet access may be slower or less reliable.[7]
Mirror sites were heavily used on the early internet, when most users accessed throughdialup and theInternet backbone had much lower bandwidth than today, making a geographically-localized mirror network a worthwhile benefit. Download archives such asInfo-Mac,Tucows andCPAN maintained worldwide networks mirroring their content accessible overHTTP oranonymous 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 Some of these networks, such as Info-Mac or Tucows are no longer active or have removed their mirrored download sections, but some like CPAN or theDebian package mirrors are still active in 2023.[8] Debian removed FTP access to its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 ascaching andload balancing that are available to HTTP.[9] Modern mirrors supportHTTPS and IPv6 along with IPv4.[10]
On occasion, some mirrors may choose not to replicate the entire contents of theupstream server because of technical constraints, or selecting only a subset relevant to their purpose, such as software written in a particularprogramming language, runnable on a singlecomputer platform, or written by one author. These sites are calledpartial mirrors orsecondary mirrors.[11]
It was once common for tech companies such asMicrosoft,Hewlett-Packard orApple to maintain a network of mirrors accessible over HTTP or anonymous FTP, hostingsoftware updates,sample code and various freely-downloadableutilities. 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 useweb scraping software to producestatic dumps of existing sites, such as the BBC'sTop Gear and RedFlagDeals.
^"Debian worldwide mirror sites".Archived from the original on 6 September 2017. Retrieved27 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. Retrieved11 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. Retrieved11 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. Retrieved21 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. Retrieved27 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. Retrieved11 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.
