Shareware is commercially available software that is distributed freely and shared among users, with the expectation that a user will pay for use of the software after evaluating it to determine that the software meets the user's needs.

This model of software distribution was first introduced in the 1980s, with popularity rising through the 1990s. Popular software like PKZip, for example, were originally released as shareware.

The distribution model has proven to work since, as there is no upfront cost to try shareware, it encourages users to try products users might not have otherwise considered due to cost and unknown performance.

The distribution model is now widely used for software delivered over the Internet, where many commercial software providers offer products to download for free and expect payment later. Most such products have a trial period of 30 to 90 days.