A software license is a legal instrument governing the use or redistribution of software.
Since the 1970s, software copyright has been recognized in the United States. Despite the copyright being recognized, most companies prefer to sell licenses rather than copies of the software because it enables them to enforce stricter terms on redistribution. Very few purchasers read any part of the license, initially shrink-wrap contracts and now most commonly encountered as clickwrap or browsewrap. The enforceability of this kind of license is a matter of controversy and is limited in some jurisdictions. Service-level agreements are another type of software license where the vendor agrees to provide a level of service to the purchaser, often backed by financial penalties.