Taylor Swift is exclusively releasing her '1989' documentary on Apple Music

On Sunday, Taylor Swift turned 26 - and she used her birthday to make a surprise announcement.

Swift's upcoming 1989 World Tour documentary will be released exclusively on Apple Music, Swift said in an Instagram post.

"Thank you so much for all the birthday wishes!" she wrote on Instagram, accompanied by a teaser trailer for the documentary. "I have a little surprise for you. The 1989 World Tour Live. Directed by Jonas Akerlund. Released on @applemusic December 20, 2015."

Apple Music users will be able to stream the documentary for free.

Earlier this year Swift publicly sparred with Apple. In June, the singer refused to put her most recent album, "1989," on Apple Music.

"I'm sure you are aware that Apple Music will be offering a free 3 month trial to anyone who signs up for the service. I'm not sure you know that Apple Music will not be paying writers, producers, or artists for those three months," Swift said in a Tumblr post at the time, justifying her decision. "I find it to be shocking, disappointing, and completely unlike this historically progressive and generous company." 

Her opinion was enough to catch the attention of Apple Music's Eddy Cue. Apple said it would change its policy and would pay artists royalties. Swift said she was "elated and relieved" upon Cue's announcement on Twitter at the time.

"Apple Music will pay artists for streaming even during customers' free trial period," Cue tweeted. "We hear you @taylorswift13 and indie artists. Love, Apple."

Taylor Swift has been an outspoken critic of free music streaming. She argues that it devalues artists' work, and she removed "1989" from market-leader Spotify late last year following a dispute over its free, ad-supported tier.

You can watch the trailer below: