It is not the Guardian's first account to pass the mark, with @GuardianTech already attracting more than 2 million followers, helped by both being in Twitter's 'suggested users' list in the early days, and arguably by the technology audience being big users of Twitter.
Journalism.co.uk has been speaking to Laura Oliver, community manager at the Guardian, to find out the how the @Guardian account is managed, how it attracts new followers, and to gather some tips on growing a Twitter community.
Managing the account
The @Guardian account is "highly managed" by the community team, Oliver explained. There are three community coordinators who manage the account, with one person focusing on it at any given time between about 8am and 7pm on weekdays. At other times the account is managed by other editorial teams in London and by the US team. Some scheduling also takes place, with the community coordinators using HootSuite to push out content at key times.
The community coordinators "identify stories they think will play well for the Twitter audience, identify stories that need to go out at different times of day depending on what geographic audience we are trying the attract", Oliver said. They are constantly "looking at the language we use, looking at how we cover breaking news events with this account, and how we recommend our journalists and the site sections we have".
Analytics and editors
The community team use their own judgement as to how to write tweets that will encourage retweets and interactions and use Twitter's own analytics tool.
"We look at analytics, we look at referrals from our social accounts and try and set ourselves baseline stats," Oliver said. "So looking at what is a typical response to a tweet, for example, and how we measure against that. We are still in the early days of that process but our community team is certainly very attuned to looking at that kind of information to make decisions."
Gathering 1 million followers
So how did @Guardian grow to attract 1 million followers? It launched in 2009, so was not particularly early to the Twitter party.
"It has a very distinct voice," Oliver said. And it is a voice that the team thought long and hard about when in late 2010 the Guardian first employed community coordinators to manage some of the Twitter accounts, as well as to manage other communities and feedback to the editorial teams on potential stories, sources and angles.
"We sat down and talked about the persona behind the account," Oliver said. "What language would we use and wouldn't we use in particular situations? What communities elsewhere on the web would we like it to reach and contact?"
The team also planned "takeovers", where a Guardian journalist takes over a Twitter account for a specific period of time around an event or in the case of breaking news.
And planning is something that happens on a daily and weekly basis. "There's quite a lot of thought that goes into that not just on a day-to-day basis but across the week, and particularly into the weekends where our content can have a lot of long-tail value as well."
The approach to managing @Guardian is not only to push out one or two stories an hour, it is also social. "Our team spend a lot of time replying to our followers, asking them questions, seeding content with them, encouraging them to get involved," Oliver said.
Involvement is something the team is pushing for by carrying out a crowdsourcing exercise that coincides with reaching the 1 million milestone. "It's a great opportunity for us to find out who we have got following us and who we haven't, perhaps where we are not getting to and who is not picking us up."
The social approach also sees the team promoting not only different sections of the Guardian, but also individual reporters covering a particular story, plus contributors, such as some of the people who send images to GuardianWitness, a recent development in crowdsourcing at the Guardian.
When asked for her tips, Oliver stressed the importance of planning. "A lot of the most successful projects that we run involving these accounts, whether crowdsourcing or callouts or promoting new features or series on the site, have been planned in advance," she said.
"We are very much of the school of thought that it's not 'if you build it they will come', instead a lot of thought goes into which account to use." And as part of that planning they are continuously asking questions such as: "Who have we got following us already? Who do we need to build up in advance who will be interested in this feature? How can we keep them with us after this series has finished?"
The non-automated approach takes time but does provide highly engaged followers, Oliver said. "It's not a surprise for me that the Guardian accounts that are handpicked are successful, because a lot of love and effort goes into them every single day."
She added: "It is incredibly labour-intensive at times but it brings us a great deal of success in terms of the model of journalism that we are following, which is that we want people to be in conversation with us, we want there to be engagement, we want people to have their say and for us to be able to talk directly back to them."
For more on editorially managed Twitter accounts see: Lessons from Auntie as @BBCNews goes human.
Before joining the Guardian, Laura Oliver was editor of Journalism.co.uk.