Social media app Bluesky is growing at incredible speed - driven in no small part with dissatisfaction with Elon Musk's X (formerly known as Twitter).
The user base on the app has surged from nine million in September to more than 19 million by mid-November, with the site sometimes gaining a million users per day and often being the most-downloaded app in the Apple app store.
High profile figures including Stephen King, Jamie Lee Curtis and Barbra Streisand have left Twitter/X in recent days, with King saying, "The atmosphere has just become too toxic." Media organisations such as The Guardian have also left the platform.
Bluesky is a microblogging network not dissimilar to Twitter/X, but is 'decentralised' - meaning users can host their own data if they want.
In practice, most people do not do this, and to use and look at, Bluesky is very, very similar to Twitter.
It's also relatively new, having been invitation-only until February of this year.
Unlike Twitter, users are free to set up their own servers and communities on Bluesky - on Twitter, everything is centralised and controlled by Twitter.
Bluesky also has more options for users to control what content that they see on the platform.
For example, users can create 'custom feeds' and tweak their main feed by adding topics, or specialised lists like 'Popular with Friends'.
Bluesky has more security and privacy features, such as the ability to set profiles 'private' and end-to-end encryption for messages, which means that even Bluesky cannot 'read' messages sent on the platform.
The company has also confirmed it will not use Bluesky posts to 'train' artificial intelligence models, something which Twitter already does.
Bluesky is also currently ad-free.
Social media and marketing consultant Kellie Whitehead told Yahoo News: "Anecdotally, most people sharing their move to Bluesky, ironically via their X accounts are stating the lack of moderation, new platform policy, toxic rhetoric and harmful content.
"In my feed, it's the shifting political and social landscape leading X users to seek alternatives that align more closely with their values, especially in light of controversies surrounding content moderation policies on Twitter. Whilst Bluesky isn't new, the US election result and discourse around it has driven the user base away in numbers this past fortnight."
Bluesky lists are one of the tools the platform offers to help users customise their feeds, by building up and sharing public lists of posters.
To use it, select the bullet-pointed list icon in your app or browser, then select New.
To add users to a list, select their profile, then the three-dot icon next to it, then 'Add to list'.
Sky Follower Bridge is a tool for browsers such as Chrome which allows users to automatically migrate their Twitter/X 'following' list to BlueSky.
To use it, add the Follower Bridge plugin to your browser.
Then go to either your Twitter/X following or followers page, and with the page open, press Alt-B.
This scans your follower/following list for Bluesky users and lets you decide whether to follow them on Bluesky.
Bluesky was founded by former Twitter chief Jack Dorsey, who originally came up with the idea in 2019.
Dorsey stepped down from the board in 2024 and has deleted his account.
Bluesky is now run and owned by chief executive Jay Graber.
Many celebrities have joined Bluesky in recent months, including Lizzo, Stephen King, Guillermo del Toro, Ben Stiller and others.
Grammy winning Lizzo said last week: "I hate the internet. Anyways I joined bluesky cus we're leaving toxicity in 2024."
British TV comedian Greg Davies has also joined Bluesky after writing on X last week: "Hello all, I'll be leaving X in the next few days. Thanks for the lovely messages over the years."
CEO Graber has said the platform is gaining roughly 10,000 new users every 15 minutes.
The platform gained a million users in the week after the US election, following Musk's high-profile support for Donald Trump.