Misplaced Pages

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47-634: The technology behind the World Wide Web, the Hypertext Transfer Protocol (HTTP), does not make any distinction of types of links—all links are functionally equal. Resources may be located on any server at any location. When a website is visited, the browser first downloads the textual content in the form of an HTML document. The downloaded HTML document may call for other HTML files, images, scripts and/or stylesheet files to be processed. These files may contain <img> tags which supply

94-439: A batch of RFCs was published, deprecating many of the previous documents and introducing a few minor changes and a refactoring of HTTP semantics description into a separate document. HTTP is a stateless application-level protocol and it requires a reliable network transport connection to exchange data between client and server. In HTTP implementations, TCP/IP connections are used using well-known ports (typically port 80 if

141-486: A client user interface called web browser . Berners-Lee designed HTTP in order to help with the adoption of his other idea: the "WorldWideWeb" project, which was first proposed in 1989, now known as the World Wide Web . The first web server went live in 1990. The protocol used had only one method, namely GET, which would request a page from a server. The response from the server was always an HTML page. In 1991,

188-474: A client failing to properly encode the request-target. Since 2016 many product managers and developers of user agents (browsers, etc.) and web servers have begun planning to gradually deprecate and dismiss support for HTTP/0.9 protocol, mainly for the following reasons: In 2020, the first drafts HTTP/3 were published and major web browsers and web servers started to adopt it. On 6 June 2022, IETF standardized HTTP/3 as RFC   9114 . In June 2022,

235-722: A communications network. An application layer abstraction is specified in both the Internet Protocol Suite (TCP/IP) and the OSI model . Although both models use the same term for their respective highest-level layer, the detailed definitions and purposes are different. In the Internet protocol suite, the application layer contains the communications protocols and interface methods used in process-to-process communications across an Internet Protocol (IP) computer network. The application layer only standardizes communication and depends upon

282-471: A copy of the images for purposes of the Copyright Act. In other words, Google does not have any "material objects...in which a work is fixed...and from which the work can be perceived, reproduced, or otherwise communicated" and thus cannot communicate a copy. Instead of communicating a copy of the image, Google provides HTML instructions that direct a user's browser to a website publisher's computer that stores

329-421: A far future version of HTTP called HTTP-NG (HTTP Next Generation) that would have solved all remaining problems, of previous versions, related to performances, low latency responses, etc. but this work started only a few years later and it was never completed. In May 1996, RFC   1945 was published as a final HTTP/1.0 revision of what had been used in previous 4 years as a pre-standard HTTP/1.0-draft which

376-528: A globally routable address, by relaying messages with external servers. To allow intermediate HTTP nodes (proxy servers, web caches, etc.) to accomplish their functions, some of the HTTP headers (found in HTTP requests/responses) are managed hop-by-hop whereas other HTTP headers are managed end-to-end (managed only by the source client and by the target web server). HTTP is an application layer protocol designed within

423-536: A server establishing a connection (real or virtual). An HTTP(S) server listening on that port accepts the connection and then waits for a client's request message. The client sends its HTTP request message. Upon receiving the request the server sends back an HTTP response message, which includes header(s) plus a body if it is required. The body of this response message is typically the requested resource, although an error message or other information may also be returned. At any time (for many reasons) client or server can close

470-403: A short time, or in more complex setups, to allow the hotlinking but return an alternative image with reduced quality and size and thus reduce the bandwidth load when requested from a remote server. All hotlink prevention measures risk deteriorating the user experience on the third-party website. The most significant legal fact about inline linking, relative to copyright law considerations, is that

517-465: A single Google webpage, the Copyright Act...does not protect a copyright holder against [such] acts.... Hypertext Transfer Protocol This is an accepted version of this page HTTP ( Hypertext Transfer Protocol ) is an application layer protocol in the Internet protocol suite model for distributed, collaborative, hypermedia information systems. HTTP is the foundation of data communication for

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564-540: Is a revision of previous HTTP/2 in order to use QUIC + UDP transport protocols instead of TCP. Before that version, TCP/IP connections were used; but now, only the IP layer is used (which UDP, like TCP, builds on). This slightly improves the average speed of communications and to avoid the occasional (very rare) problem of TCP connection congestion that can temporarily block or slow down the data flow of all its streams (another form of " head of line blocking "). The term hypertext

611-556: Is realized by the use of the functionality of a number of application service elements. Some application service elements invoke different procedures based on the version of the session service available. The common application service element sublayer provides services for the application layer and request services from the session layer. It provides support for common application services, such as: The specific application service element sublayer provides application-specific services (protocols), such as: The IETF definition document for

658-401: Is required. HTTP/3 , the successor to HTTP/2, was published in 2022. As of February 2024, it is now used on 30.9% of websites and is supported by most web browsers, i.e. (at least partially) supported by 97% of users. HTTP/3 uses QUIC instead of TCP for the underlying transport protocol. Like HTTP/2, it does not obsolete previous major versions of the protocol. Support for HTTP/3

705-501: Is used by more than 85% of websites. HTTP/2 , published in 2015, provides a more efficient expression of HTTP's semantics "on the wire". As of August 2024, it is supported by 66.2% of websites (35.3% HTTP/2 + 30.9% HTTP/3 with backwards compatibility) and supported by almost all web browsers (over 98% of users). It is also supported by major web servers over Transport Layer Security (TLS) using an Application-Layer Protocol Negotiation (ALPN) extension where TLS 1.2 or newer

752-403: The OSI model , the definition of the application layer is narrower in scope. The OSI model defines the application layer as only the interface responsible for communicating with host-based and user-facing applications. OSI then explicitly distinguishes the functionality of two additional layers, the session layer and presentation layer , as separate levels below the application layer and above

799-468: The URLs which allow images to display on the page. The HTML code generally does not specify a server, meaning that the web browser should use the same server as the parent code ( <img src="picture.jpg" /> ). It also permits absolute URLs that refer to images hosted on other servers ( <img src="http://www.example.com/picture.jpg" /> ). When a browser downloads an HTML page containing such an image,

846-519: The United States Court of Appeals for the Ninth Circuit explained why inline linking did not violate US copyright law: Google does not...display a copy of full-size infringing photographic images for purposes of the Copyright Act when Google frames in-line linked images that appear on a user's computer screen. Because Google's computers do not store the photographic images, Google does not have

893-413: The World Wide Web , where hypertext documents include hyperlinks to other resources that the user can easily access, for example by a mouse click or by tapping the screen in a web browser . Development of HTTP was initiated by Tim Berners-Lee at CERN in 1989 and summarized in a simple document describing the behavior of a client and a server using the first HTTP version, named 0.9. That version

940-422: The client whereas a process , named web server , running on a computer hosting one or more websites may be the server . The client submits an HTTP request message to the server. The server, which provides resources such as HTML files and other content or performs other functions on behalf of the client, returns a response message to the client. The response contains completion status information about

987-719: The HTTP Working Group released an updated six-part HTTP/1.1 specification obsoleting RFC   2616 : In RFC   7230 Appendix-A, HTTP/0.9 was deprecated for servers supporting HTTP/1.1 version (and higher): Since HTTP/0.9 did not support header fields in a request, there is no mechanism for it to support name-based virtual hosts (selection of resource by inspection of the Host header field). Any server that implements name-based virtual hosts ought to disable support for HTTP/0.9 . Most requests that appear to be HTTP/0.9 are, in fact, badly constructed HTTP/1.x requests caused by

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1034-463: The URL for inline links, even though it is a frequent security complaint. Embedded images may be used as a web bug to track users or to relay information to a third party. Many ad filtering browser tools will restrict this behavior to varying degrees. Some servers are programmed to use the HTTP referer header to detect hotlinking and return a condemnatory message, commonly in the same format, in place of

1081-484: The browser will contact the remote server to request the image content. The ability to display content from one site within another is part of the original design of the Web's hypertext medium. Common uses include: The blurring of boundaries between sites can lead to other problems when the site violates users' expectations. Other times, inline linking can be done for malicious purposes. Most web browsers will blindly follow

1128-444: The connection is unencrypted or port 443 if the connection is encrypted, see also List of TCP and UDP port numbers ). In HTTP/2, a TCP/IP connection plus multiple protocol channels are used. In HTTP/3, the application transport protocol QUIC over UDP is used. Data is exchanged through a sequence of request–response messages which are exchanged by a session layer transport connection. An HTTP client initially tries to connect to

1175-516: The connection. Closing a connection is usually advertised in advance by using one or more HTTP headers in the last request/response message sent to server or client. In HTTP/0.9 , the TCP/IP connection is always closed after server response has been sent, so it is never persistent. Application layer An application layer is an abstraction layer that specifies the shared communication protocols and interface methods used by hosts in

1222-416: The establishment of TCP connections presents considerable overhead, especially under high traffic conditions. HTTP/2 is a revision of previous HTTP/1.1 in order to maintain the same client–server model and the same protocol methods but with these differences in order: HTTP/2 communications therefore experience much less latency and, in most cases, even higher speeds than HTTP/1.1 communications. HTTP/3

1269-601: The expected image or media clip. Most servers can be configured to partially protect hosted media from inline linking, usually by not serving the media or by serving a different file. URL rewriting is often used (e.g., mod_rewrite with Apache HTTP Server ) to reject or redirect attempted hotlinks to images and media to an alternative resource. Most types of electronic media can be redirected this way, including video files, music files, and animations (such as Flash ). Other solutions usually combine URL rewriting with some custom complex server side scripting to allow hotlinking for

1316-443: The first documented official version of HTTP was written as a plain document, less than 700 words long, and this version was named HTTP/0.9, which supported only GET method, allowing clients to only retrieve HTML documents from the server, but not supporting any other file formats or information upload. Since 1992, a new document was written to specify the evolution of the basic protocol towards its next full version. It supported both

1363-727: The framework of the Internet protocol suite . Its definition presumes an underlying and reliable transport layer protocol. In HTTP/3 , the Transmission Control Protocol (TCP) is no longer used, but the older versions are still more used and they most commonly use TCP. They have also been adapted to use unreliable protocols such as the User Datagram Protocol (UDP), which HTTP/3 also (indirectly) always builds on, for example in HTTPU and Simple Service Discovery Protocol (SSDP). HTTP resources are identified and located on

1410-461: The full-size photographic image. Providing these HTML instructions is not equivalent to showing a copy. First, the HTML instructions are lines of text, not a photographic image. Second, HTML instructions do not themselves cause infringing images to appear on the user's computer screen. The HTML merely gives the address of the image to the user's browser. The browser then interacts with the computer that stores

1457-502: The group stopped its activity passing the technical problems to IETF. In 2007, the IETF HTTP Working Group (HTTP WG bis or HTTPbis) was restarted firstly to revise and clarify previous HTTP/1.1 specifications and secondly to write and refine future HTTP/2 specifications (named httpbis). In 2009, Google , a private company, announced that it had developed and tested a new HTTP binary protocol named SPDY . The implicit aim

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1504-426: The infringing image. It is this interaction that causes an infringing image to appear on the user's computer screen. Google may facilitate the user's access to infringing images. However, such assistance raised only contributory liability issues and does not constitute direct infringement of the copyright owner's display rights. ...While in-line linking and framing may cause some computer users to believe they are viewing

1551-531: The inline linker does not place a copy of the image file on its own Internet server. Rather, the inline linker places a pointer on its Internet server that points to the server on which the proprietor of the image has placed the image file. This pointer causes a user's browser to jump to the proprietor's server and fetch the image file to the user's computer. US courts have considered this a decisive fact in copyright analysis. Thus, in Perfect 10, Inc. v. Amazon.com, Inc. ,

1598-458: The need to start to focus on a new HTTP/2 protocol (while finishing the revision of HTTP/1.1 specifications), maybe taking in consideration ideas and work done for SPDY. After a few months about what to do to develop a new version of HTTP, it was decided to derive it from SPDY. In May 2015, HTTP/2 was published as RFC   7540 and quickly adopted by all web browsers already supporting SPDY and more slowly by web servers. In June 2014,

1645-748: The network by Uniform Resource Locators (URLs), using the Uniform Resource Identifiers (URIs) schemes http and https . As defined in RFC   3986 , URIs are encoded as hyperlinks in HTML documents, so as to form interlinked hypertext documents. In HTTP/1.0 a separate TCP connection to the same server is made for every resource request. In HTTP/1.1 instead a TCP connection can be reused to make multiple resource requests (i.e. of HTML pages, frames, images, scripts , stylesheets , etc.). HTTP/1.1 communications therefore experience less latency as

1692-447: The new versions of browsers and servers was rapid. In March 1996, one web hosting company reported that over 40% of browsers in use on the Internet used the new HTTP/1.1 header "Host" to enable virtual hosting , and that by June 1996, 65% of all browsers accessing their servers were pre-standard HTTP/1.1 compliant. In January 1997, RFC   2068 was officially released as HTTP/1.1 specifications. In June 1999, RFC   2616

1739-811: The request and may also contain requested content in its message body. A web browser is an example of a user agent (UA). Other types of user agent include the indexing software used by search providers ( web crawlers ), voice browsers , mobile apps , and other software that accesses, consumes, or displays web content. HTTP is designed to permit intermediate network elements to improve or enable communications between clients and servers. High-traffic websites often benefit from web cache servers that deliver content on behalf of upstream servers to improve response time. Web browsers cache previously accessed web resources and reuse them, whenever possible, to reduce network traffic. HTTP proxy servers at private network boundaries can facilitate communication for clients without

1786-417: The simple request method of the 0.9 version and the full GET request that included the client HTTP version. This was the first of the many unofficial HTTP/1.0 drafts that preceded the final work on HTTP/1.0. After having decided that new features of HTTP protocol were required and that they had to be fully documented as official RFCs , in early 1995 the HTTP Working Group (HTTP WG, led by Dave Raggett )

1833-618: The transport layer. OSI specifies a strict modular separation of functionality at these layers and provides protocol implementations for each. In contrast, the Internet Protocol Suite compiles these functions into a single layer. Originally the OSI model consisted of two kinds of application layer services with their related protocols. These two sublayers are the common application service element (CASE) and specific application service element (SASE). Generally, an application layer protocol

1880-495: The underlying transport layer protocols to establish host-to-host data transfer channels and manage the data exchange in a client–server or peer-to-peer networking model. Though the TCP/IP application layer does not describe specific rules or data formats that applications must consider when communicating, the original specification (in RFC   1123 ) does rely on and recommend the robustness principle for application design. In

1927-460: Was added to Cloudflare and Google Chrome first, and is also enabled in Firefox . HTTP/3 has lower latency for real-world web pages, if enabled on the server, and loads faster than with HTTP/2, in some cases over three times faster than HTTP/1.1 (which is still commonly only enabled). HTTP functions as a request–response protocol in the client–server model . A web browser , for example, may be

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1974-499: Was already used by many web browsers and web servers. In early 1996 developers started to even include unofficial extensions of the HTTP/1.0 protocol (i.e. keep-alive connections, etc.) into their products by using drafts of the upcoming HTTP/1.1 specifications. Since early 1996, major web browsers and web server developers also started to implement new features specified by pre-standard HTTP/1.1 drafts specifications. End-user adoption of

2021-459: Was coined by Ted Nelson in 1965 in the Xanadu Project , which was in turn inspired by Vannevar Bush 's 1930s vision of the microfilm-based information retrieval and management " memex " system described in his 1945 essay " As We May Think ". Tim Berners-Lee and his team at CERN are credited with inventing the original HTTP, along with HTML and the associated technology for a web server and

2068-482: Was constituted with the aim to standardize and expand the protocol with extended operations, extended negotiation, richer meta-information, tied with a security protocol which became more efficient by adding additional methods and header fields . The HTTP WG planned to revise and publish new versions of the protocol as HTTP/1.0 and HTTP/1.1 within 1995, but, because of the many revisions, that timeline lasted much more than one year. The HTTP WG planned also to specify

2115-433: Was released to include all improvements and updates based on previous (obsolete) HTTP/1.1 specifications. Resuming the old 1995 plan of previous HTTP Working Group, in 1997 an HTTP-NG Working Group was formed to develop a new HTTP protocol named HTTP-NG (HTTP New Generation). A few proposals / drafts were produced for the new protocol to use multiplexing of HTTP transactions inside a single TCP/IP connection, but in 1999,

2162-694: Was subsequently developed, eventually becoming the public 1.0. Development of early HTTP Requests for Comments (RFCs) started a few years later in a coordinated effort by the Internet Engineering Task Force (IETF) and the World Wide Web Consortium (W3C), with work later moving to the IETF. HTTP/1 was finalized and fully documented (as version 1.0) in 1996. It evolved (as version 1.1) in 1997 and then its specifications were updated in 1999, 2014, and 2022. Its secure variant named HTTPS

2209-463: Was to greatly speed up web traffic (specially between future web browsers and its servers). SPDY was indeed much faster than HTTP/1.1 in many tests and so it was quickly adopted by Chromium and then by other major web browsers. Some of the ideas about multiplexing HTTP streams over a single TCP/IP connection were taken from various sources, including the work of W3C HTTP-NG Working Group. In January–March 2012, HTTP Working Group (HTTPbis) announced

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