Software update is the process of changing installed software with the intent to make it more modern. It also refers to the stored data used to update software. When storage was significantly more expensive, patching files was the dominant form of update. With the advent of larger distribution storage media and higher Internet bandwidth, it became common to replace entire files instead of patching.

This article is about software updates in general. For the discontinued macOS component, see Apple Software Update.

An update may require prior application of other updates, or may require prior or concurrent updates to multiple components. To facilitate updates, operating systems often provide automatic or semi-automatic updating facilities. Package management systems and app stores can offer update automation.

An update can be any size. An update can be relatively large when the changes add or replace data such as graphics and sound files, for example for a game update. An update usually takes less time to run than an initial installation of the software.

Although often intended to upgrade, an update may instead degrade. An update may include unintentional regression problems. In some cases, an update intentionally disables functionality, for instance, by removing aspects for which the consumer is no longer licensed.