2015 has seen a crazy amount of great album releases, and it's no different in the realm of mixtapes. With all the albums that have been released, you might actually forget all the fantastic projects artists have dropped for free online.

Mixtapes are a difficult format to be successful in. Dozens (maybe even hundreds) are uploaded to various websites every day, and most just get lost in the shuffle, only to be heard by a handful of people. While mixtapes can be and have been used to skyrocket a new artist to stardom, many of the most notable tapes in a given year are released by artists with existing audiences. These releases serve as a collection of tracks that didn't make the final album or an expression of gratitude to the fans. Oftentimes it's both. Sometimes a good mixtape can even outshine an artist's official studio albums.

While compiling the list of top mixtapes of the year, we kept in mind critical acclaim as well as popularity. Some listed projects are from incredibly popular artists that got thousands (even millions) of downloads, while others are lesser known, but high-quality compilations from new and rising artists.

Sometimes the label of mixtape can be confusing, especially when albums are fully released on the internet for free. This list doesn't contain free albums like that, which excludes projects like Donnie Trumpet & The Social Experiment's Surf. It also has to be free, which excludes Drake's If You're Reading This, It's Too Late, even though that project has been described as a mixtape.

So without further ado, here are the 20 Best Mixtapes of 2015.

Check out the 20 Best Hip-Hop Albums of 2015