How to cite an archived page: what to record so others can find the same capture

Why a live link is not enough

Web pages change and disappear. The US Supreme Court says some URLs cited in its opinions may change over time or disappear altogether, so it attempts to capture the cited material in PDF format ¹. It lists these captures on a page titled Online Sources Cited in Opinions ¹.

Perma.cc, developed and maintained by the Harvard Law School Library, says that in a sample of several legal journals about 70% of links in citations published between 1999 and 2011 no longer pointed to the same material ². Perma.cc archives a page a user enters and returns a link to the preserved copy ².

What to record

A citation to an archived page should let a reader reach the same capture. The elements below come from how archives identify captures.

• The original URL of the page, which Memento calls the Original Resource ⁴.
• The full archived URL. On the Wayback Machine it contains the capture code, as in web.archive.org/web/20000229123340/http://www.yahoo.com/ ³.
• The capture date and time as the archive states it. The Wayback example above was crawled on 29 February 2000 at 12:33:40 ³.
• The name of the archive, such as the Internet Archive's Wayback Machine or Perma.cc ^2,3.
• The date you viewed the capture, as captures can be excluded or removed later. The Internet Archive reviews exclusion requests and may disable access to content ^3,5.

Getting the capture time right

The capture time is not the time you asked for. Under RFC 7089 a TimeGate returns the memento closest to the requested datetime, and archives are often sparse, so the result can differ noticeably from the request ⁴. The Memento-Datetime header is the value to cite ⁴.

The Internet Archive says replacing the capture code in a Wayback URL with an asterisk lists every capture of a site ³. Choosing a specific capture from that list and citing its full URL avoids ambiguity.

The capture time shows when the archive copied the page. It does not show when the page was first published. The European Patent Office tells examiners that archiving services can help date a web page, and that the Internet Archive's incompleteness does not detract from the credibility of what it holds ⁶.

Making your own capture

The Wayback Machine's Save Page Now feature saves a specific page one time. It does not save whole sites or add the URL to future crawls ³. A capture appears in the Wayback Machine 3 to 10 hours after a crawl, by the Internet Archive's account ³.

Perma.cc offers free accounts through registrars such as academic institutions and courts, and paid subscriptions for law firms, publishers and individuals ².

Citing a capture as evidence

A citation in a paper is not the same as proof in court. In United States v. Gasperini, decided on 2 July 2018, the Second Circuit accepted Wayback screenshots after an Internet Archive witness explained how the Archive works and compared them with its records ⁷. A full archived URL and capture time let such a witness locate the record.