Threads, Mark Zuckerberg's Instagram-based challenge to dethrone Elon Musk's troubled Twitter, has already secured tens of millions of downloads, but it remains to be seen whether this Twitter rival will be a winning one.
What is it?
Threads is a text-based sidekick of Instagram, the image-heavy social network that Facebook bought more than a decade ago and became the world's most popular app for photo sharing.
You can't be a Threads user without being signed up to Instagram and Zuckerberg said that he ultimately aims to reach one billion users, or about half Instagram's current base.
The app is easily downloadable from Instagram, where users need just a few clicks to replicate their account on the new platform. This has propelled Threads to become the fastest downloaded app ever on Apple's app store.
Once signed in, users have the same handle and inherit the same followers as they have on Instagram.
Verified accounts on Instagram are also verified on Threads, but be careful: you can only delete a Threads account by getting rid of your Instagram one, too.
Is it the same as Twitter?
If you don't like Twitter -- and many people don't -- you won't like Threads either, as the user interface is generally speaking very similar.
Zuckerberg joked about this in a meme tweet on Musk's platform, his first in 12 years, that featured an unexpected encounter between two identical superheros.
Users are allowed 500 characters in each post, can add a picture, five minutes of video and make replies, similar to the basic building blocks of Twitter.
But at this stage Threads is missing some key ingredients like search, hashtags, and a following only feed, meaning what you see is generated by an algorithm -- not who you follow.
Instagram boss Adam Mosseri said his teams were "cranking away" to provide more features as quickly as possible.
Why not Europe?
The birth of Threads comes just as a series of landmark laws governing big tech are coming into force in the European Union, including the Digital Markets Act (DMA).
The DMA will govern so-called internet gatekeepers such as Meta, and one of the rules bans giants from combining personal data across several products, as would be the case with Threads and Instagram.
Mosser said the problems with Europe were just too large and that any solution would be "months and months away."
What about the data?
Meta's history with the handling of personal data is checkered and the company formerly known as Facebook is always on the search to win back trust, all while maximizing its huge profits.
At the root of the problem is Meta's revenue generator, targeted advertising which feeds off heavy intakes of personal data through Meta's platforms but also when tracked beyond them.
Threads' terms of service double down on Meta's business model, asking users to offer the site a wide berth to closely track their internet usage, something that will be very difficult for European regulators to let through.
Who's in, who's out
Like gaining entrance to a hot new night club, a group of celebrities, journalists and companies were offered an early VIP access to Threads, helping liven up its opening hours.
Singers Shakira and Jennifer Lopez, basketball player Stephen Curry, creator Pharrell Williams and talk show icon Oprah Winfrey have already joined Threads and posted several messages.
Netflix, Spotify, Amazon and Coca-Cola have all opened official Threads accounts.
But some of Instagram's biggest account holders have yet to adopt the sister site. Lionel Messi, Dwayne Johnson, Justin Bieber and Beyonce have yet to venture to Threads.