The chunk file format defines a means of storing class definitions and other Smalltalk expressions to a text file. Such files can later be filed back into an image by choosing the File/File In menu command available in most of the development tools.

As well as archiving the definition of a class, chunk files are also a useful medium for distributing code, especially to developers with other Smalltalk implementations. The PAC and PAX files associated with Dolphin's packaging system are also in chunk format.