2016: The Year in Charts

Justin Bieber Joins Diplo & Skrillex at Hard Summer Fest: Watch

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Justin Bieber performs at 102.7 KIIS FM's Wango Tango at StubHub Center on May 9, 2015 in Los Angeles, California. 

A surprise Justin Bieber performance was in store for fans at this weekend's Jack Ü (Diplo and Skrillex) set at Los Angeles’ HARD Summer Festival. 

HARD Summer 2015 Day 1 Recap: The Weeknd, Chemical Brothers & More Highlight Opening Night

The Biebs hopped on stage, leading the crowd in his Jack Ü collaboration "Where Are Ü Now." Watch the performance -- and the audience excitement -- below. 

Justin Bieber and Skrillex are both hitting Billboard's Hot 100 Festival this Aug. 22-23. Check out the full lineup here and get tickets here

Billboard Hot 100 Fest