The term shareware (also known as trialware or demoware) refers to proprietary software that is provided to users without payment on a trial basis and is often limited by any combination of functionality, availability or convenience. Shareware is often offered as a download from an Internet website or as a compact disc included with a periodical such as a newspaper or magazine. The rationale behind shareware is to give buyers the opportunity to use the program and judge its usefulness before purchasing a license for the full version of the software. Firms with superior software thus have an incentive to offer samples, except if their product is already well known, or if they do not want to be listed in direct competition with other products on shareware repositories.

Shareware is usually offered either with certain features only available after the license is purchased, or as a full version but for a limited trial period of time. Once the trial period has passed the program may stop running until a license is purchased. Shareware is often offered without supports or updates which only become available with the purchase of a license. The words "free trial" or "trial version" are indicative of shareware.

The term shareware is used in contrast to retail software, which refers to commercial software available only with the purchase of a license which may not be copied for others, public domain software, which refers to software not copyright protected, and freeware, which refers to copyrighted software for which the author solicits no payment (though he or she may request donations).