New York (CNN Business) Social media dominated the top apps of the year.

On Tuesday, Apple unveiled its list of the most downloaded iPhone apps of 2018. Topping the list is YouTube, followed by Instagram, Snapchat, Messenger and Facebook, respectively.

Bitmoji — a Snapchat-owned app that lets users create an emoji that looks like them — dropped to sixth place on the list. It was the most downloaded app last year.

It's been a challenging year for some social media companies, such as Facebook, which has faced criticism over privacy issues, data misuse, misinformation and election meddling on its platform. Nevertheless, Facebook's flagship app and two others owned by the company (Instagram and Messenger) made the top five on the most downloaded list.

Snapchat also faced challenges this year, including navigating a controversial redesign that was widely panned by users, and heightened competition from Instagram — which has copied many of its popular features.

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