Although copying an entire work will ordinarily militate against a finding of fair use,^1538 one
could argue that caching inherently requires copying all or a substantial portion of the cached
material in order to derive the benefits of the caching, and this factor should therefore not be
dispositive of fair use.
For example, the Netcom court noted that “the mere fact that all of a work is copied is not
determinative of the fair use question, where such total copying is essential given the purpose of
the copying.”^1539 Because Netcom had copied no more of the plaintiff’s works than necessary to
function as a Usenet server, the court concluded that the third statutory factor should not defeat
an otherwise valid defense.^1540
OSPs that engage in copying of whole works may be able to rely on this logic by arguing
that such copying is essential given the nature and purpose of caching. Such an argument may,
however, be vulnerable to attack, depending upon the way in which the caching is performed.
Caching by an OSP of only that material that has been requested by users in some previously
defined time period may be said to be “essential” because such material has at least a
demonstrated basis for expecting that it will be accessed again. But what about extensive
“mirroring,” where an OSP copies, for example, entire websites from geographically remote sites
to more local servers? Such caching is not based on actual demand usage. Should this matter?
Could the OSP argue that such caching is “essential” to avoid potential network bottlenecks from
the remote site to its users’ computers? The case of Field v. Google, discussed in Section
III.B.4(a) below, found extensive caching by Google using automated robots to be a fair use.
(d) Effect of Use on the Potential MarketThe fourth statutory fair use factor looks to the effect of the use upon the potential market
for or value of the copyrighted work. This factor is generally considered the most important of
the four factors.^1541 In analyzing this factor, a court may look to “‘whether unrestricted and
widespread conduct of the sort engaged in by the defendant ... would result in a substantially
adverse impact on the potential market’ for the original.”^1542 Because caching is inherently
widespread on the Internet, a court may well look beyond the individual actions of a particular
caching entity and assess the potential aggregate impact of caching on a copyright owner.
The application of this factor is very difficult to predict in advance, without knowing the
particular factual circumstances of the caching that is being challenged. There are no doubt
many instances of caching that do not harm the potential market for a copyright owner’s work,
(^1538) Sony Corp. v. Universal Studios, Inc., 464 U.S. 417, 449-50 (1984).
(^1539) Netcom, 907 F. Supp. at 1380 (citing the Supreme Court’s decision in Sony, in which the Court held that total
copying of copyrighted broadcast programs for the purpose of time-shifted viewing was a fair use).
(^1540) Netcom, 907 F. Supp. at 1380.
(^1541) See 4 M. Nimmer & D. Nimmer, Nimmer on Copyright § 13.05[A][4], at 13-180 to –181 (1999) (citing, inter
alia, Harper & Row, Publishers, Inc. v. Nation Enterprises, 471 U.S. 539, 566 (1985)).
(^1542) Campbell v. Acuff-Rose Music, Inc., 114 S. Ct. 1164, 1177 (1994) (quoting 3 M. Nimmer & D. Nimmer,
Nimmer on Copyright § 13.05[A][4]).