The Wayback Machine is a digital time capsule created by the Internet Archive non-profit organization, based in San Francisco, California. It is maintained with content from Alexa Internet. The service enables users to see archived versions of web pages across time, which the Archive calls a "three dimensional index". Internet Archive bought the domain waybackmachine.org for their own site. It is currently in its beta test.

The name Wayback Machine is a reference to a segment from The Rocky and Bullwinkle Show in which Mr. Peabody and Sherman use a time machine called the "WABAC machine" to witness, participate in, and, more often than not, alter famous events in history.

In 1996, Brewster Kahle, with Bruce Gilliat, developed software to crawl and download all publicly accessible World Wide Web pages, the Gopher hierarchy, the Netnews bulletin board system, and downloadable software. The information collected by these "crawlers" does not collect all the information available on the Internet since much of the data is restricted by the publisher or stored in databases that are not accessible. These "crawlers" also respect the robots exclusion standard for websites wishing to opt-out of appearing in search results or being cached. To overcome inconsistencies in partially cached websites, Archive-It.org was developed in 2005 by the Internet Archive as a means of allowing institutions and content creators to voluntarily harvest and preserve collections of digital content, and create digital archives.