Jennifer Aniston may have broken the Guinness World Record for the fastest account to gain one million Instagram followers, but the Friends star has revealed she still doesn't know why she joined the social media platform.

On Tuesday, the Hollywood star finally acquiesced and joined Instagram after previously insisting she would not have a social media account.

Her delightful first post was a selfie of her and her Friends co-stars Lisa Kudrow, Courteney Cox, Matt LeBlanc, David Schwimmer and Matthew Perry.

Aniston appeared on Jimmy Kimmel Live! on Wednesday where she discussed her record-breaking start on Instagram. 

She racked up a million followers in five hours and 16 minutes, surpassing Prince Harry and Meghan Markle's previous record. Her current follower count stands at 12 million.

"It's crazy," the 50-year-old star said, describing herself as "the most reluctant person to join Instagram."

When Kimmel said "You don't do that kind of stuff", she quipped "Well I do now!"

On being asked why she joined, she said "I don't know," before joking "I'm just trying to build content."

Aniston's initial post was so popular that it caused issues for Instagram, with some users unable to follow her profile.

She followed up her first post by uploading a jokey video of herself smashing her phone with the caption: "I swear I didn't mean to break it... Thank you guys for the kind, glitchy welcome."

The actress previously revealed that fellow Hollywood A-lister and her This Morning Show co-star Reese Witherspoon made some convincing arguments about joining the social networking site.

"You can actually have a little bit more control over the narrative that's out there," Aniston said.

"[You can] right some wrongs and some silly things that, God knows, are said often."

Aniston and Witherspoon's upcoming series This Morning Show will debut exclusively on Apple TV Plus in the autumn.

For more television news click here