If you are just trying to make mixes for playing offline, you can use producing software like Reaper. You can be a lot more creative since you have more audio p

If you are just trying to make mixes for playing offline, you can use producing software like Reaper. You can be a lot more creative since you have more audio processing tools available, like adding compressors to equalize the volume to make it sound better everywhere. If you are trying to dj in a performance sense, you really need a controller. When mixing songs into one another, there is often 2/3 things you have to do at once which is hard to do without dedicated knobs. But in this case, software really doesn't matter for basic functionality. As other said, mixxx is very good, and is very customizable - you can write javascript for any control. The paid software have a few more features, namely stems, which allow you to isolate vocals/instrumental/drums on the fly (whereas before you had to have separate tracks for each), which can make mixes sound a little bit clearer. For complete info, if you are really trying to get into DJing from a performance standpoint, I highly recommend a standalone controller, namely Denon Prime Go.