Methods, systems, and apparatus, including computer programs encoded on computer storage media, for captive runtime deployment. In one aspect, a method performed by data processing apparatus employing a runtime environment includes accessing software code of a software application that relies on a runtime of the runtime environment to operate; selecting a proper subset of the runtime, including sharable library code, based on information associated with the software application; combining the software code and the proper subset of the runtime to form a computer program configured to effect the software application using a version of the runtime captive to the computer program, the captive version of the runtime including the proper subset of the runtime; and storing the computer program on a computer-readable medium coupled with a processor.