Delta update

A delta update is a software update that requires the user to download only those parts of the software's code that are new, or have been changed from their previous state, in contrast to having to download the entire program. The use of delta updates can save significant amounts of time and computing bandwidth. The name "delta" derives from the mathematical science use of the Greek letter delta, Δ or δ to denote change.

Another name for the underlying technology is binary delta compression. In any case, the combination of the old version and the downloaded delta is used to reconstruct the new version. For information on the technology used to produce the differences, see data differencing.