backport

Backport is a software maintenance practice in which a fix, improvement, or feature implemented in a newer version of a software project is adapted and applied to an older release line. The goal is to provide the benefits of the change to users who are on that older version without requiring them to upgrade to the latest release. This is common in projects with long-term support or stable branches, and in environments where upgrading is costly or impractical.

Backporting is frequently used for security patches and critical bug fixes, as well as for parity of functionality between releases. The process typically involves identifying the patch in the newer version, isolating the change so it can be applied to the target older version, resolving any API or dependency differences, and validating through testing to ensure no regressions are introduced. In some cases, the backported change must be rewritten or split into smaller patches to fit the older codebase.

Backporting carries risks, including conflicts with past changes, API drift, and increased maintenance overhead. It may also delay the release cycle of the older branch if substantial testing or refactoring is needed. To manage these risks, teams often rely on cherry-picking commits, dedicated backport branches, and automated testing pipelines, and they document the scope and limitations of each backport.

Common examples include the Linux kernel's stable branches, which receive security fixes from the mainline, or enterprise software that maintains long-term support versions. Backporting differs from forward porting, which moves changes from older to newer releases, rather than older to older.