Publication Date



Consumer contracts are a pervasive legal tool that govern
many of our daily activities. Yet, consumer contracts are
routinely modified by businesses after customers accept them.
Common modifications include, for example, a change in fees,
alteration of a dispute resolution clause, or revision to the firm’s
privacy policy. In fact, unilateral modifications can affect
virtually every aspect of a contract.
While the literature widely discusses the problem of ex ante
consent to consumer contracts, it does not adequately address
the problem of ex post consent to unilateral modifications. But
the practice of unilateral changes to consumer form contracts
comes with significant detriments and social costs. Despite
these costs, there are no systematic empirical studies exploring
this phenomenon. This Article aims to fill this gap by
empirically examining the frequency, mechanics, and degree of
transparency of unilateral change mechanisms in consumer
This Article examines 500 sign-in-wrap contracts of the most
popular websites in the United States that use such agreements.
We find that the vast majority of consumer contracts in our
sample are “sneak in” contracts—that is, they allow firms

unilateral and broad discretion to covertly change consumers’
rights and obligations after consumers accept them. This
study’s findings raise concerns as to whether sneak in contracts
are aligned with prominent core values and principles of
contract law, such as consent, promise, reliance, consideration,
freedom, choice, empowerment, and community. The study thus
calls for greater transparency in the law that governs the
modification of consumer contracts.