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Text of the page (random words):
http 451 wikipedia jump to content main menu main menu move to sidebar hide navigation main page contents current events random article about wikipedia contact us contribute help learn to edit community portal recent changes upload file special pages search search appearance donate create account log in personal tools donate create account log in contents move to sidebar hide top 1 usage toggle usage subsection 1 1 additional uses 2 other usages 3 example 4 in media 5 see also 6 references 7 external links toggle the table of contents http 451 20 languages العربية català čeština dansk deutsch español فارسی suomi français עברית 日本語 한국어 bahasa melayu polski português русский српски srpski türkçe українська 中文 edit links article talk english read edit view history tools tools move to sidebar hide actions read edit view history general what links here related changes upload file permanent link page information cite this page get shortened url switch to legacy parser print export download as pdf printable version in other projects wikimedia commons wikidata item appearance move to sidebar hide from wikipedia the free encyclopedia http status code a 451 status code returned by the defense distributed website to a client in pennsylvania 30 july 2018 1 http persistence compression https quic request methods options get head post put delete trace connect patch query header fields cookie etag location http referer dnt x forwarded for upgrade response status codes 301 moved permanently 302 found 303 see other 403 forbidden 404 not found 451 unavailable for legal reasons security access control methods basic access authentication digest access authentication security vulnerabilities http header injection http request smuggling http response splitting http parameter pollution v t e in http http 451 unavailable for legal reasons is a response status code that indicates that a request cannot be satisfied for legal reasons such as a web page censored by a government the code value refers to ray bradbury s 1953 dystopian novel fahrenheit 451 in which books are outlawed 2 451 provides more information than http 403 which is often used for the same purpose 3 this status code is currently a proposed standard in rfc 7725 which updated the iana http status codes registry to include 451 4 examples of situations where an 451 could be used include web pages deemed a danger to national security or web pages deemed to violate copyright privacy blasphemy laws or any other law or court order after introduction of the general data protection regulation gdpr in the european economic area eea it became common practice for websites located outside the eea to respond with 451 to eea visitors instead of trying to comply with this new privacy law for instance many regional u s news sites no longer serve web browsers from the eu 5 6 7 the rfc is specific that a 451 response does not indicate whether the resource exists but requests for it have been blocked if the resource has been removed for legal reasons and no longer exists or even if the resource has never existed but any discussion of its topic has been legally forbidden see injunction 8 some sites have previously returned http 404 missing or similar if they are not legally permitted to disclose that the resource has been removed it is used in the united kingdom by some internet service providers utilising the internet watch foundation blacklist returning a 404 message or another error message instead of showing a message indicating the site is blocked 9 10 the status code was formally proposed in 2013 by tim bray following earlier informal proposals by chris applegate 11 in 2008 and terence eden 12 in 2012 it was approved by the internet engineering task force ietf on 18 december 2015 13 it was published as in the proposed standard rfc 7725 in february 2016 usage edit a 451 error message being displayed when visiting a website in mainland china when an entity intercepts the request and returns status 451 it should include a link http header field whose value is a uri reference identifying itself the link header field must then have a rel parameter whose value is blocked by this is intended to identify the entity implementing the blocking an isp dns provider caching system etc not the legal authority mandating the block 14 at an ietf hackathon participants used a web crawler to discover that several implementations misunderstood this header and gave the legal authority instead 15 additional uses edit the meaning of a resource which cannot be served for legal reasons has been interpreted to extend beyond government censorship when content cannot be shown in the user s country due to contractual or licensing restrictions with the content owner for example a tv program may not be available to users in some countries citation needed when a publisher refuses to serve content to a user because the user s country adds regulatory requirements that the publisher refuses to comply with e g websites based outside of the eu may refuse to serve users in the eu because they do not want to comply with the gdpr citation needed other usages edit main article list of http status codes 451 ms also used by exchange activesync when either a more efficient server is available or the server cannot access the users mailbox 16 17 the client is expected to re run the http autodiscover operation to find a more appropriate server 18 example edit an american website not served to european users to avoid compliance with the gdpr http 1 1 451 unavailable for legal reasons link https search example net legal rel blocked by content type text html html head title unavailable for legal reasons title head body h1 unavailable for legal reasons h1 p this request may not be serviced in the roman province of judea due to the lex julia majestatis which disallows access to resources hosted on servers deemed to be operated by the people s front of judea p body html in media edit http 451 was mentioned by the bbc s from our own correspondent programme in 2017 as an indication of the effects of sanctions on sudan and the inability to access airbnb the app store or other western web services 19 see also edit evil bit gag order superinjunction technological fix references edit attorney general shapiro governor wolf state police successfully block access to 3d downloadable guns in pennsylvania press release pennsylvania office of attorney general 29 july 2018 flood alison 22 june 2012 call for ray bradbury to be honoured with internet error message the guardian retrieved 22 june 2012 ducklin paul 19 august 2013 http error code 451 unavailable for legal reasons naked security sophos archived from the original on 6 may 2021 retrieved 29 november 2018 hypertext transfer protocol http status code registry iana icann 13 november 2024 retrieved 3 february 2025 matt burgess 29 august 2018 the tyranny of gdpr popups and the websites failing to adapt wired retrieved 1 october 2018 more than 1 000 u s news sites are still unavailable in europe two months after gdpr took effect www niemanlab org major us news sites are still blocking europeans due to gdpr engadget 9 august 2018 retrieved 27 july 2023 bray tim february 2016 451 unavailable for legal reasons an http status code to report legal obstacles ietf sec 3 doi 10 17487 rfc7725 rfc 7725 cleanfeed org wiki open rights group if the request is for the blocked content then the proxy server will return a 404 error page to the customer arthur charles 8 december 2008 how the iwf blacklist stops you seeing the scorpions album cover technology blog the guardian tcp reset is sent back to the customer instead of content applegate chris 9 december 2008 there is no http code for censorship qwghlm co uk archived from the original on 19 april 2021 retrieved 23 december 2015 byrne michael 21 december 2015 the http 451 error code for censorship is now an internet standard vice retrieved 3 july 2020 nottingham mark 18 december 2015 why 451 mnot s blog retrieved 20 december 2015 bray tim february 2016 identifying blocking entities an http status code to report legal obstacles ietf sec 4 doi 10 17487 rfc7725 rfc 7725 stéphane bortzmeyer 11 november 2017 rfc errata report ietf tools retrieved 3 december 2018 ms ascmd section 3 1 5 2 2 msdn microsoft com archived from the original on 26 march 2015 retrieved 8 january 2015 bradhugh exchange activesync returned an http 451 error connectivity analyzer learn microsoft com retrieved 5 august 2026 ms oxdisco msdn microsoft com archived from the original on 31 july 2014 retrieved 8 january 2015 sally hayden 28 september 2017 from our own correspondent radio bbc radio 4 external links edit media related to http 451 at wikimedia commons rfc 7725 an http status code to report legal obstacles retrieved from https en wikipedia org w index php title http_451 oldid 1371688551 categories hypertext transfer protocol status codes internet censorship hidden categories articles with short description short description is different from wikidata use dmy dates from october 2020 all articles with unsourced statements articles with unsourced statements from february 2025 commons category link from wikidata this page was last edited on 27 august 2026 at 22 06 utc page was rendered with parsoid text is available under the creative commons attribution sharealike 4 0 license additional terms may apply by using this site you agree to the terms of use and privacy policy wikipedia is a registered trademark of the wikimedia foundation inc a non profit organization privacy policy about wikipedia disclaimers contact wikipedia legal safety contacts code of conduct developers statistics cookie statement mobile view search search toggle the table of contents http 451 20 languages add topic