Proposal To Establish HTTP Status Code 451 For Websites Blocked By Censorship

By Darren Smith, Weekend Contributor

ietf-logoWith the increasing frequency of government censorship and take-down orders blocking content hosted on web servers, a consortium of internet stakeholders has proposed to the IETF an RFC Draft (recently published) proposing a standard error response given to clients that the web page or resource sought has been blocked for legal reasons.

The proposal uses the status code 451, a reference to Ray Bradbury’s book “Fahrenheit 451”.


Most users have seen the familiar “404 Not Found” or “403 Forbidden” error messages when accessing a page that does not exist or one that has restricted access. Under the surface these HTTP (HyperText Transfer Protocol) tags regulate client and server transactions, such as page request, authentication required, OK statuses and numerous others handled by the web browser and the website it is connecting to.

A pertinent excerpt from the draft before the IETF reads as follows:


This document specifies a Hypertext Transfer Protocol (HTTP) status
code for use when a server operator has received a legal demand to
deny access to a resource or to a set of resources which includes the
requested resource.

This status code can be used to provide transparency in circumstances
where issues of law or public policy affect server operations. This
transparency may be beneficial both to these operators and to end

[RFC4924] discusses the forces working against transparent operation
of the Internet; these clearly include legal interventions to
restrict access to content. As that document notes, and as Section 4
of [RFC4084] states, such restrictions should be made explicit.

451 Unavailable For Legal Reasons

This status code indicates that the server is denying access to the
resource as a consequence of a legal demand.

The server in question might not be an origin server. This type of
legal demand typically most directly affects the operations of ISPs
and search engines.

Responses using this status code SHOULD include an explanation, in
the response body, of the details of the legal demand: the party
making it, the applicable legislation or regulation, and what classes
of person and resource it applies to. For example:

HTTP/1.1 451 Unavailable For Legal Reasons
Link: ; rel=”blocked-by”
Content-Type: text/html

Unavailable For Legal Reasons

<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>

The use of the 451 status code implies neither the existence nor non-
existence of the resource named in the request. That is to say, it
is possible that if the legal demands were removed, a request for the
resource still might not succeed.

Note that in many cases clients can still access the denied resource
by using technical countermeasures such as a VPN or the Tor network.

A 451 response is cacheable by default; i.e., unless otherwise
indicated by the method definition or explicit cache controls; see

The 451 Error Code is an improvement from the present use of 403 Forbidden or in many cases 404 Not Found because among other things it informs the user that a particular resource has been blocked for legal reasons, and gives the opportunity to explain why. Typically the information “just disappears” and returns as a 404 when requested.

Discussion was made as to why 403 Forbidden would not suffice. There are reasons for which a server will return such a request due to technical reasons, such as Directly Listing Prohibited which often displays itself when directory read permissions are not granted to unauthenticated users and an index.html or default.asp file is not provided to service the request. So in a sense 403 errors are not really suitable for human abstracts such as censorship.

It is apparent, unfortunately, that unscrupulous governments in the world will demand content be removed without notice and will view the 451 response as a latency of the original censored resource, and consequently disallowing the use of 451 error codes.  It can be used in other contexts where a resource was taken down due to the author being served a take-down notice for copyright violations, etc.

Intermediaries such as content hosting sites like social media providers can easily use this. If the content is prohibited by law, such as access to Nazi paraphernalia sold on eBay which is blocked in Germany (Which of course is another matter in of itself) the 451 can be returned to users geolocated within that country but for everyone else the page will pass through.  This at least will inform the user what happened.

Another feature would be to allow the automated spidering and indexing of the web to identify the scope of censorship and track trends and growth of the practice.

It is however disappointing that such a measure needing to be addressed with regard to content censorship becoming such a norm that an RFC needs to be made to address the problem.  Twenty years ago I never would have expected this to become the new reality.

By Darren Smith


The Internet Engineering Task Force

The views expressed in this posting are the author’s alone and not those of the blog, the host, or other weekend bloggers. As an open forum, weekend bloggers post independently without pre-approval or review. Content and any displays or art are solely their decision and responsibility.

38 thoughts on “Proposal To Establish HTTP Status Code 451 For Websites Blocked By Censorship”

  1. What changes have occurred from the IRS targeting of conservative groups? Keep in mind these non-profit organizations were are epitome of “active” citizenship and where did their efforts take them? Now are we to expect a 451 code will do anything to make people more likely to get active? Maybe if the code came with instructions on how to make tax payments to the government to gain access to the site; maybe that will spur activism.

  2. It should be a felony crime for any bureaucrat, their contractors or a private front company to censor anything without a judicial warrant.

    It should also be a bigger felony to NOT notify those citizens or groups being censored so they can claim “legal standing” in federal court to challenge this unAmerican behavior (that violates their own oath of office as a condition of employment and authority).

    Enough is enough, censors belong in jail.

    1. RB; “Enough is enough, censors belong in jail.”

      Our silence is considered compliance and our peaceful activism is also considered compliance. There seems to be few avenues left to us. Criminals only understand one language and it’s not the law or the constitution. Criminals control our courts. They’re now nothing more than administrative courts and our states are private corporations. The U.S. government is a private corporation. I can provide links if you’re interested. Until we collectively figure out more effective ways to say NO to this OBVIOUS bullying, extortion, exploitation, blackmail and oppression this is going to continue to get worse.

      Collectively we have massive amounts of power. History shows us that when a critical tipping point is reached the people fight back and win…at least temporarily. Until we find a way to win more permanently this cycle of repression and revolution will continue as it has for eons; our entire history in fact.

      What will break this cycle should be on everyone’s mind. Sure, we can overthrow the government. That’s been done countless times, but what will take it’s place? Should we renew our vows to The Constitution and really make it work this time? We were told in so many words; “Here’s your Republic. Let’s see if you can keep it.” Many are trying to regain it and willing to die trying.

    1. Beldar – you can call him anything you like. It’s your teeth on the line.

  3. ‪Top 5 Censored News Stories From 2015‬

    5.) $425 billion dollar industry you’ve never heard of
    4.) 90% of people killed in drone strikes were not the intended target
    3.) CISPA internet censorship bill passed after being renamed CISA
    2.) The U.S. Government runs ISIS
    1.) 2015 was one of the safest years on record in the U.S. despite massive media fear campaign.

  4. 451 should differentiate between legal and unconstitutional. How about “WAKE UP. This site is blocked for unconstitutional reasons. How does it feel, bro?”

  5. Paul & davidm, You guys are on the ISP share plan

    TCP Port 451

    Here is what we know about protocol TCP Port 451. If you have information on TCP port 451 that is not reflected on this page, simply leave a comment and we’ll update our information.

    1. Jerry brings up an annoyance from the other day. I sent a response to group email (former high school classmates) and got the couple of usual bounced back addys. Then I am cleaning out my spam box and I have a msg asking me to fill out a form to be approved to be on this fellow students approved mail list. The irony of finding it in my spam box was not lost on me.

      Has anyone else run into this and if they have, how have they handled it?

      1. Paul, that kind of message is because the user has a whitelist. This is an aggressive anti-spam policy. Some people avoid unwanted messages by having emails allowed through only if they are on an approved list, known as a whitelist. By having you fill out the form, they can review who you are and decide whether to allow you on the list. Many emails are automated so the form is never filled out, resulting in the user having a lot less spam type emails to deal with.

        1. davidm – my challenge is that it will be a cold day in hell before I fill in a form to be accepted by someone.

  6. I agree with David. The codes will give some sort of a reason for why the site is not appearing. 404 means the content isn’t there….usually it is an old link to a URL or a page on a site that has been removed, expired or changed. 403 tells me that the site is still there but is restricted for some reason. Perhaps a private site that needs permission to enter. Maybe it is porn and I’m glad I don’t have permission :-0

    The new code 451 tells me that the government (most likely) or other legal issue is censoring the site. If you know the reasons, then you know how to react. As your favorite “conservative” sites get the 451 scarlet letter mark, then you know more about what the government is doing. Similar to the IRS censoring groups that they felt were in opposition to the Holy Emperor Obama during the last election, execpt they hid the actions. A 451 code would put it into the open.

  7. I like the idea because it tells the user that the information being sought is there, but I am not allowed access to it for legal reasons. The 404 means the content is not there, and the 403 means the owner of the site needs to give me login credentials to access it. So a 451 would tell me to use legal channels to get access to the content. It lets me know that government censorship is likely in play.

  8. For those who want to see the TCP/UDP ports live while using IE or Chrome browser or email, download free app Wireshark sniffer for Windows or MAC. Works on wired or wireless connections.

    You can examine the ports, 21-FTP, 22-SSH server listening, 25-SMTP mail, 53-DNS request/reply, 80-HTTP Internet traffic, 110-POP3 mail delivery, 115-SFTP secure file,
    443-SSL secure HTTP, 445 MS Active directory, 1720-video tel. Fun stuff. Call your ISP provider if you a see problem.

    1. Jerry – I just want a webpage that jumps up and says “Your government is currently watching you. This message is NOT an error.”

  9. Maybe I need more coffee this morning but I cannot see what the 451 code will accomplish. As with any other infringement of rights, government will have their teeth in deep long before anyone FEELS the pain. And once government gets what it wants it doesn’t easily give it back.

  10. Tyger,

    If RFC 2324 can be adopted and port 666 assigned to the game “Doom” then this certainly will. 🙂

  11. This is one Status Code proposal that should go through, both for the information it would provide and for the backstory reference it makes to Bradbury’s “Fahrenheit 451”, which is SO appropriate.

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