A legacy application (legacy app) is a software program that is outdated or obsolete. Although a legacy app still works, it may be unstable because of compatibility issues with current operating systems (OS), browsers and information technology (IT) infrastructures

Most enterprises use legacy applications and systems that continue to serve critical business needs. Typically, the challenge is to keep the legacy application running, while converting it to newer, more efficient code that makes use of current technology and programming languages.

Why are legacy applications still used?

Legacy software includes those that have been superseded by new versions; those built by developers who no longer maintain them, leaving the support team without the necessary depth of knowledge to do so; and those that have been patched or otherwise altered to the point of incompatibility with current standard versions.