## Sub-bundles

Bnd projects support building a single bundle per workspace project, or multiple bundles.

When building a single bundle, all data about both the project (e.g. the build path) and about the output bundle (such as private packages, exported packages, service components, etc) is included in the `bnd.bnd` file.

However when building multiple bundles, the `bnd.bnd` file only contains the project configuration. Information about the output bundles is held in separate files called, e.g., `something.bnd`. These files are called sub-bundles.

When switching from a single-bundle project to a multiple-bundle project, it is often necessary to move some instructions from the `bnd.bnd` file into the new sub-bundle file.