Linkback


A linkback is a method for Web authors to obtain notifications when other authors link to one of their documents. This enables authors to keep track of who is linking to, or referring to, their articles. The four methods differ in how they accomplish this task.
"LinkBack" is the generalized term used to reference four methods of communication between websites.
Any of the four terms—Linkback, Trackback, Pingback, or Refback—might also refer colloquially to items within a section upon the linked page that display the received notifications, usually along with a reciprocal link; Trackback is used most often for this purpose. Also, the word Trackback is often used colloquially to mean any kind of Linkback.
RefbackTrackbackPingbackWebmention
Trigger mechanismVisitor to linking site clicks on the link, and their browser takes them to the linked siteCode on linking server examines added or updated documents, extracts links, and sends notification to linked server for each link foundCode on linking server examines added or updated documents, extracts links, and sends notification to linked server for each link foundCode on linking server examines added or updated documents, extracts links, and sends notification to linked server for each link found
Notification mediumHTTP referrer valueHTTP POSTXML-RPC callHTTP POST with source and target parameters
Capture mechanismExamination of incoming HTTP referrer valuesTrackback capture scriptXML-RPC functionWebmention capture script
Information sent by linking server-
  • Linking site name '
  • Linking post title '
  • Linking post excerpt
  • Linking post URL
  • Linked post URL
  • Linking post URL
  • Linked post URL
  • Linking post URL
    • Additional information presented to linked serverHTTP referrer sent by a visitor's browser upon clicking the linkIP address of linking serverIP address of linking serverIP address of linking server
    Autodiscovery mechanism -LINK tag in the header of the linked page or Trackback RDF DocumentsSpecial HTTP header or LINK tag on the linked pageHTTP Link header or link element on the linked page
    Action required when notification is received
  • Extract referrer value from incoming HTTP headers
  • Retrieve referring page
  • Parse retrieved page for desired information
  • Gather desired information from
  • * Given parameters
  • * or retrieving and parsing the given URL
  • Retrieve page at "linking post URL"
  • Parse retrieved page for desired information
    		• Verifying that linking page does indeed link to linked page is recommended, not explicitly required
    AdvantagesRequires no special code on linking server All the information desired by the linked server is present in the notification itself
  • Notification mechanism has a complete technical specification
  • Less susceptible to spamming
  • Uses well-known parts of HTTP wherever possible
  • Reuses Pingback's existing semantics
  • Minimum amount of data transferred on-the-wire
    • Disadvantages
  • No notification unless someone actually clicks on the link
  • Relies upon visitors' browsers sending proper HTTP referrer information
  • Linked site must retrieve and parse linking site's page to extract the information it wants
  • Notification requires positive action by linking server
  • Notification mechanism has only a partial technical specification
  • Autodiscovery information may prevent XHTML validation
  • Notification requires positive action by linking server
  • Linked site must retrieve and parse linking site's page to extract the information it wants
  • Can be abused for DDOS attacks
  • Relatively new, so less widely implemented.