In software development, a warm body is a developer working on a project who may or may not be helpful to the project. They are referred to as such because they appear to fulfil only the absolute minimum requirements for working on the project - i.e. by exaggeration, they are not actually dead.

When a software project starts to fall behind schedule, one idea is to add more people; i.e. warm bodies, to it. In theory this should increase the rate of progress on the project. It is a well-known (though unfortunately frequently ignored) phenomenon of development that this is not always the case. The problem is related to the mythical man-month, first popularised in Fred Brooks' book The Mythical Man-Month. In other words, you cannot work out the length of a project by taking the number of man-months of effort and dividing by the number of people on the project.

There are several reasons why adding a warm body to a project is not always helpful. If the new developer is not familiar with the tools and techniques being used in the project, then they will need time to learn them. Input from existing team members is almost always required in order to bring the newcomer up to speed, and this reduces the effort being put into the project. In even worse cases the newcomer can make mistakes (due to insufficient knowledge) which have to be fixed by established team members. Newcomers often do not have the necessary skills to contribute to the project - it is this kind of person who is generally referred to as a 'warm body'.

Even if the newcomer is generally familiar with the main tools and techniques, virtually all projects have a body of knowledge, or specific procedures, unique to that project. Thus the newcomer will add very little value in the short term. If the time-to-completion of the project is short, adding even a highly skilled person can delay it further.

Even if the newcomer were to understand perfectly all the knowledge and procedures of the team, adding a person increases the communication overhead. Information must now be communicated to more people; meetings will take that much longer; misunderstandings will take that much longer to clarify and correct.

Even when a perfectly skilled and knowledgeable newcomer is added to a team, tasks must be reassigned and possibly re-subdivided. It can also be true that some tasks are not subdivisable, so that the newcomer has no prospect of speeding those tasks up. As the management maxim goes, "You cannot make a baby in a month by impregnating nine women."

Adding warm bodies to attempt to increase the speed of a project is an example of an anti-pattern.