JS minifiers are programs that reduce the size of JS files by removing all the unnecessary characters. This includes comments, white space, and new line characters. JS minifiers can also rename variables and functions to shorter names, reducing the file size. Although JS minifiers can significantly reduce the size of JS files, they can also make the code difficult to read and debug. For this reason, it is essential only to use JS minifiers when necessary. However, when used properly, JS minifiers can help improve JS applications' performance.