An ASAR file is an archive used to package source code for an application using Electron, an open source library used to build cross-platform programs. It is saved in a format similar to .TAR archives where files contained in the archive, such as .HTML, .JS, and .CSS files, are concatenated together without using compression.

ASAR files allow developers to package their apps in an archive instead of a folder, which protects the source code of the app from being exposed to other users. You can package the application into an archive using the asar utility included with Electron.