Fanfiction is when a writer takes the story and/or characters from a book, TV show, movie, comic, video game, or other work and repurposes them in their own story without owning the original content. There are multiple archives that host fanfiction from multiple sources and genres such as: FanFiction, Archive of Our Own, Kindle Worlds, and WattPad.

Pros

Fanfiction can have a benefit for both the original author and the fanfiction writer. The benefit depends on the quality of the fanfiction as well-written fanfiction has the largest benefit for the original author and the writer of the fanfiction.  

The original writer of the content that fanfiction is based upon can benefit from the popularity of the fanfiction as it can increase the sales of the original work and merchandise. In addition, it also keeps the original work fresh in the minds of the fan between sequels and even when the series has come to an end. For example, Harry Potter fanfiction (which is legal to write as long as it is not pornographic) kept numerous fans interested in the Harry Potter series between the release of the films and books. The fanfiction kept the fans interested and allowed the fanfiction fans and writers to make predictions about what the next book or film would include in a way that kept all the fans entertained.

Fanfiction can also prove to be a benefit to the fanfiction writer if that person then goes on to write and publish original content, as most fanfiction sites allows the writer to create a profile where he or she can post links to original content that they are selling. If the fanfiction proves to be enjoyable to a reader, then the reader might want to seek out and purchase original works that belong to the writer. In this matter, fanfiction can be a great way for a reader to assess the writing style of the writer and decide if it is to the reader's liking without having to make a purchase.

Cons

Fanfiction can likewise prove to be detrimental to both the original author and the fanfiction writer. The detriment depends on the quality of the fanfiction as poorly written fanfiction, obscene elements, and pornography can put readers off the original work and the fanfiction writer’s future work.

Fanfiction that is done badly can hurt the original author of the work as it could result in readers of that fanfiction becoming less interested, disgusted, or hateful towards the original work, depending on the content of the fanfiction. Even with a disclaimer stating the fanfiction is not official, damage can be done to the image of the original piece due to the emotions of the reader.

The writer of a bad piece of fanfiction can also suffer if he or she is looking to become or is a published author as the readers of the fanfiction might be disinclined to have anything to do with the works of the fanfiction write. However, unlike the author of the work the fanfiction is based upon, the fanfiction writer is able to avoid most of these detrimental elements by writing under a pen name and not including links to other published works.