The buildbot is a port build service which builds ports using the MacPorts Buildbot (MPBB) scripts.

Every time a maintainer commits changes to MacPorts' ports Git repository the buildbot will check whether a rebuild of the corresponding port(s) would be necessary. If the port(s) in question are distributable their binary archives will be kept for subsequent distribution for all versions of the Mac operating system for which build machines are available. See the list of builders to find out which platforms these currently are.

If a build error occurred for a port its maintainer will be informed via an email so that problems which did not surface on the maintainer's machine will not go unnoticed.

Thus the buildbot helps to keep MacPorts consistent on various macOS versions, i.e., a maintainer does not need access to these versions anymore in order to assure that the port(s) maintained build without problems. Currently only the default port variants will be built and kept.

The web page at build.macports.org offers several views of the recent builds and of their success. Port maintainers will find the waterfall and the builders views most useful, since they give information about the build status and offer the possibility to build one's port(s) on specific builders.

Also, a web page at ports.macports.org provides an alternate view of buildbot activity. Enter the name of the port you are interested in. That takes you to a summary page, which shows the success or failure of the last recorded build on each OS version. See the "Port Health" indicators near the top. Click on those indicators to to see a description of the latest build on build.macports.org. Click the Build Information tab to see all recorded builds.