Memento Project

Memento is a United States National Digital Information Infrastructure and Preservation Program (NDIIPP)–funded project aimed at making Web-archived content more readily discoverable and accessible to the public.

Technical description
Memento is defined in RFC 7089 as an implementation of the time dimension of content negotiation. HTTP accomplishes negotiation of content via a variety of headers that allow clients and servers to find content that the user desires.

The Last-Modified header provided by HTTP does not necessarily reflect when a particular version of a web page came into existence. Also, the Last-Modified header may not exist in some cases. To provide more information, the Memento-Datetime header has been introduced to indicate when a specific representation of a web page was observed on the web.



Usage
Copies of page can be found by simply navigating, in a web browser, to a link formatted, replacing   with the full URL of the page desired:

JSON description of a Memento:
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redirect to a Memento with a datetime that is close to a desired datetime: