patchlevel

Patchlevel is a numeric indicator used in software versioning to designate the level of bug fixes and security patches applied to a release after its initial release. It helps distinguish between releases that share the same major and minor version but differ in the set of fixes included. The patchlevel is typically increased whenever a new patch is released, such as a bug fix backport or a security update, and is usually independent of feature changes.

In practice, patchlevel appears in version strings in various forms. Some projects append it as a separate field (for example, 2.4.6p3 or 2.4.6-3), while others maintain a standard semantic versioning scheme with a PATCH component (1.2.3). The patchlevel may be tracked internally, in changelogs, or in build metadata, rather than being visible in all user-facing versions.

Relation to other versioning schemes: under semantic versioning, the PATCH component corresponds to backwards-compatible bug fixes. Patchlevel can be considered a historical or project-specific label; in many contexts it is closely related to the PATCH part of the version, while in others it serves as an additional tag used by the release process.

Impact and usage: Patchlevel increments signal that fixes or security updates are included without introducing new features or breaking changes. For users, upgrading to a higher patchlevel usually aims to improve stability and security, though the exact effect depends on the project’s release practices.