Any of the four terms -- Linkback, Trackback, Pingback, or (rarely) 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.
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| Refback
| Trackback
| Pingback
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| Trigger mechanism
| Visitor to linking site clicks on the link, and his browser takes him to the linked site
| Code on linking server examines added or updated documents, extracts links, and sends notification to linked server for each link found
| Code on linking server examines added or updated documents, extracts links, and sends notification to linked server for each link found
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| Notification medium
| HTTP referer value
| HTTP POST
| XML-RPC call
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| Capture mechanism
| Examination of incoming HTTP referer values
| Trackback capture script
| XML-RPC function
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| Information sent by linking server
| None
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- Linking site name (Optional)
- Linking post title (Optional)
- Linking post excerpt (Optional)
- Linking post URL
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- Linked post URL
- Linking post URL
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| Additional information presented to linked server
| HTTP referer sent by a visitor's browser upon clicking the link
| IP address of linking server
| IP address of linking server
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| Autodiscovery mechanism (how the linking server finds out how and where to send the notification)
| None
| Specially-formatted information within the body of the linked page
| Special HTTP header or LINK tag on the linked page
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| Action required when notification is received
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- Extract referrer value from incoming HTTP headers
- Retrieve referring page
- Parse retrieved page for desired information
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- Gather desired information from
- Given parameters
- or retrieving and parsing the given URL
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- Retrieve page at "linking post URL"
- Parse retrieved page for desired information
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| Advantages
| Requires no special code on linking server (the link itself becomes the notification when someone clicks on it)
| All the information desired by the linked server (Linking site name, post title, excerpt) is present in the notification itself
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- Notification mechanism has a complete technical specification
- Less susceptible to spamming
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| Disadvantages
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- No notification unless someone actually clicks on the link
- Relies upon visitors' browsers sending proper HTTP referer information
- Linked site must retrieve and parse linking site's page to extract the information it wants
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- Notification requires positive action by linking server
- Notification mechanism has only a partial technical specification
- Autodiscovery information may prevent XHTML validation
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- Notification requires positive action by linking server
- Linked site must retrieve and parse linking site's page to extract the information it wants
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