This page in a nutshell: Because of the potential for abuse and technical limitations on the MediaWiki software, open proxies may be blocked from editing for any period at any time.

This page provides information about the use of open proxies to read and edit the English Wikipedia.

Open or anonymizing proxies, including Tor, may be blocked from editing for any period at any time. While this may affect legitimate users, they are not the intended targets and may freely use proxies until those are blocked. No restrictions are placed on reading Wikipedia through an open or anonymous proxy.

Proxies are left open due to deliberate or inadvertent configuration or because crackers have changed the configuration. Non-static IP addresses or hosts that are otherwise not permanent proxies should typically be blocked for a shorter period of time, as it is likely the IP address will eventually be transferred or dynamically reassigned, or the open proxy closed. Once closed, the IP address should be unblocked.

To maintain project security, administrators reviewing blocks involving open proxies should not unblock the IP address or range in question unless they are sure that there is no longer a functioning open proxy at that location. For assistance with this, administrators are encouraged to list the IP address/range at Wikipedia:WikiProject on open proxies/Requests for review.

Although Wikipedia encourages anyone in the world to contribute, open proxies are often used abusively. MediaWiki, the wiki software that powers Wikipedia, depends on IP addresses for administrator intervention against abuse, especially by unregistered users. Open proxies allow malicious users to change IP addresses rapidly, causing continuous disruption that cannot be stopped by administrators. Several such attacks have occurred on Wikimedia projects, causing disruption and occupying administrators who would otherwise deal with other concerns.

This policy is known to cause difficulty for some editors, who must use open proxies to circumvent censorship where they live; for example, editors in countries where Wikipedia is censored, such as China, should sign up for free access to Wikipedia-only proxies at Wikipedia:WikiProject on closed proxies or read Wikipedia:Advice to users using Tor to bypass the Great Firewall. Additionally, because of the creation of the IP block exemption flag, editors, like those in China, who have a demonstrated need to use proxies or Tor to edit may be given the ability to edit from blocked IPs. See Wikipedia:IP block exemption for more.

When a Checkuser detects that an account has been using open proxies, this information may be considered when evaluating suspicions of sock puppetry or other editing abuses. If there is an appearance that an account has been using open proxies to circumvent policy, the account may be blocked.

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