When Facebook paid $1 billion for Instagram back in 2012, some people thought that Mark Zuckerberg's company may have spent too much for the photo- and video-sharing app. But today Instagram passed the half a billion users milestone, proving yet again that the acquisition was a good deal.

Out of its 500 million users - 80 percent of which live outside the US - two-thirds (300 million) are using Instagram every day. It sees an average of 95 million daily photo and video uploads, with around 4.2 billion "likes."

Instagram now boasts roughly double the number of daily active users (DAU) of its closest rival, Snapchat, which has around 150 million DAUs. News of its rapidly increasing popularity will no doubt be a blow to Twitter, which continues to lag behind with about 136 million DAUs.

Facebook, meanwhile, continues to see almost two billion people accessing its network each day, and its $19 billion acquisition of WhatsApp is also looking like a bargain, as the messaging app recently passed one billion registered users.

It seems the visual overhaul that Instagram received last month hasn't had any negative impact, despite the changes not being universally loved. Gone is the classic, skeuomorphic-style icon, replaced with a flatter, more colorful image. The UI was also updated so it consists of mostly white and gray with the text showing in black. Instagram said it wants the only color to come from the content users upload.

It was last September when Instagram reported it had surpassed the 400 million users milestone. At this rate, it's quickly catching up with that other incredibly popular Facebook-owned application, Messenger.

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