What Is Sub4Sub? Sub4Sub, or ‘sub for sub’, is the practice of subscribing to somebody else’s channel in exchange for them subscribing to yours. Whether Sub4Sub works is very debatable as people say it’s good, and others say it’s bad, however, it is fairly popular. At the end of the day, it’s really one of the worst things to do. See below for the full post!Why “Sub4Sub” on YouTube is BAD | NEVER Do SUB4SUB!