Mike Isaac has used Bluesky since shortly after it launched last year.
In February 2023, a half-dozen techies introduced a social network prototype in an invitation-only launch. They deliberately debuted their creation, Bluesky, with little fanfare so that they could closely manage its growth.
But lately, it has been anything but slow and steady.
Over the past week, Bluesky's growth has exploded, more than doubling to 15 million-plus users as people seek alternatives to X, Facebook and Threads. It has rocketed to the top of Apple's and Google's app stores as the most downloaded free app. Its ascent has been so rapid that the company has been forced to grow up practically overnight.
Bluesky's 20 full-time employees have been working around the clock to deal with the issues that come with hyper-growth: site outages, glitches in the code and content moderation issues. Most importantly, they have been trying to keep early users happy as new members have flooded in.
"We as a team take pride in our ability to scale quickly," Jay Graber, 33, the chief executive of Bluesky, said in an interview. "But there's always some growing pains." She added that the app -- which is still dwarfed by Facebook, Instagram and X -- was adding more than one million new users a day.
Bluesky is surging amid upheaval in the social media world. After Elon Musk bought Twitter in 2022, he morphed it into X, changing many of its functions and alienating some of its most loyal users. Threads, an app similar to X that Meta introduced last year, relies mostly on an opaque algorithmic curation that excises politics from people's feeds. That has caused some people to head to other networks, including Bluesky, to discuss hot-button social issues.
From its beginning, Bluesky aimed to separate itself from other social media. The project grew out of an idea from Jack Dorsey, a founder of Twitter, who said he hoped to build a "decentralized" social network.
That meant building the app with an "open protocol," which keeps the social network's power and decision making out of the hands of any one company or group of people. Mr. Dorsey called the project "Bluesky," and it eventually became a public benefit corporation, a type of for-profit company that aims to have a positive impact on society rather than focus on maximizing shareholder value.
Bluesky was initially financed with a grant from Twitter under Mr. Dorsey; Mr. Musk cut ties with the Bluesky team after he bought Twitter. Bluesky later raised more than $23 million in two rounds of venture funding from private investors.
From there, a team of about a half dozen, led by Ms. Graber, began building the "AT protocol." That is a technical term for the code that would essentially let independent developers create their own social networks atop it, while allowing people to carry their digital identities and information across different platforms. Using this technology, Bluesky executives say, people can tailor their own algorithms to show themselves the kinds of social media posts they want to see.
In contrast, Facebook and TikTok lock people into their platforms and make it difficult for them to migrate to competitors. The apps are known as "walled gardens," meaning that what is posted on individual platforms remains only on that platform. (In March, Meta loosened this stance by allowing users to turn on an option that syndicates their Threads posts to other social networks, like Mastodon.)
With Bluesky, "you're no longer tied to a dominant algorithm that promotes either the most polarizing posts and/or the biggest brands," Rose Wang, Bluesky's chief operating officer, said in a recent video explaining the site to new users. She added, "It's built by the people, for the people."
Bluesky gained traction after Mr. Musk began making major changes to X, including promoting accounts that paid for "blue check" verification status and eliminating content moderation rules. As he put fewer limits on speech across X, some people sought a less noxious online atmosphere in Bluesky.
In September, Bluesky's popularity rose after X was banned in Brazil when Mr. Musk refused to comply with a court order to suspend certain accounts. More than three million people joined Bluesky during the three weeks that X was banned in the country, before Mr. Musk reversed course.
The last week and a half has been an inflection point. Since Donald J. Trump won the presidential election, some X users have abandoned the platform because of Mr. Musk's close ties with Mr. Trump. Often they have flocked to Bluesky.
More than 116,000 people in the United States deactivated their X accounts on the web the day after the election -- the most U.S. deactivations in a single day under Mr. Musk -- according to data compiled by Similarweb, which analyzes websites. Total deactivations could be much higher because Similarweb does not track how many users deactivated their mobile X app accounts.
As people gravitated to Bluesky, problems piled up. The site went down at times on Thursday, causing new users to frantically refresh until it came back online. Ms. Graber said the glitches were partly due to issues with a major internet service provider that also affected other sites. Bugs persisted, including one that affected how user names were displayed in profiles.
New users clashed with existing ones. Some new users complained that Bluesky users were too earnest, a reflection of a different era of social media. Early adopters bristled, saying the newbies needed to adapt to Bluesky's social norms.
"Every time there's a big influx in users in general, everyone expects it to be like the last place they came from," said Chris Vinson, 33, a digital marketer from Evansville, Ind., who has used Bluesky since its early days. "They want it to be the new Twitter or whatever, even if it isn't supposed to be."
Ms. Graber referred to the culture clash as the "eternal September" problem, an allusion to how universities turn over their student population every year, resulting in drastic changes to the culture.
Her solution has been to build more features into the app, such as allowing people to create custom feeds based on different topics or groups, and to build up automated content moderation tools that can hide or remove posts that break Bluesky's rules, such as harassment, incitement to violence or hate speech.
Rivals have taken notice. Last week, Adam Mosseri, the head of Instagram, noted that Threads had added more than 15 million new users -- or an entire Bluesky -- in the first half of November. Mark Zuckerberg, Meta's chief executive, said on Friday that Threads would test ways for users to create their own custom feeds, copying one of Bluesky's popular features.
Ms. Graber is positioning Bluesky as a David taking on Goliaths by differentiating itself further. On Friday, the company said it would never use people's posts to train generative artificial intelligence technology, a contrast to practices at Meta, X and Google.
She said she hoped that independent developers could build atop Bluesky's technology to make the social network even better. That's different from Facebook and X, which have had hot-and-cold relationships with the developer community.
"The state of most social platforms right now is that users are locked in and developers are locked out," Ms. Graber said. "We want to build something that makes sure users have the freedom to move and developers have the freedom to build."
"Fundamentally, we did this because we want to build an ecosystem that developers can put their trust in, and if anyone has an idea for improving the state of social media, they don't have to lobby us to change things," she added. "They can just do it themselves."