Scenes from DreamHack, where 23,000 gamers spend a weekend plugged in together.

The best historical analogy for the ‘‘hackathon’’ might be the 18th-­century custom of the barn-­raising. Despite the technological abyss separating the two rituals, they are structurally akin: Each is a social observance in which a lot of people focus their collective will on an undertaking too great for any individual to carry out alone. Though the informal practice of hackathons arose slightly earlier, the first use of the portmanteau name dates to 1999, when Sun Microsystems and the freeware operating system OpenBSD each staged events under that banner to write very specialized pieces of software very quickly.

Over time, the sense of the term has expanded; one count estimates that in 2015 there will be more than 1,500 gatherings branded as hackathons, with this summer alone offering events designed to plan for Australia’s aging population, conserve water in India and streamline the resale of tickets at Wimbledon. There are hackathons for television technologies, life sciences and political causes — the term these days is used anywhere people congregate with the expectation of getting something vaguely machine-­oriented done in one big room.

The world’s largest recurring convention of people and their machines is DreamHack, a 72-hour rally that takes place twice a year in the convention center in Jonkoping, Sweden, a lake city about 200 miles southwest of Stockholm. The most recent jamboree hosted more than 23,000 people from at least 55 nations and every inhabited continent; on their 9,500 computers (as well as 14,000 other network-­connected devices), the attendees made up what organizers believe to be the largest impromptu LAN, or local area network, assembled anywhere.

DreamHack began in 1994, in the basement of a nearby elementary school, as a small, local subvariant of what was then called a ‘‘copy­party’’ — pre-­broadband occasions to share software or demonstrate flashy off-­label uses of early home computers. As the event has grown, its enormous ad hoc network has been given over largely to gaming; for far-flung clans of four or five teammates, this can be the only chance they get all year to palaver in person. But participants also use the LAN to collaborate on all manner of projects, from songs to films to digital artworks, all of which are presented to the crowd.

click to view the complete set of images in the archive

This feature was commissioned by The New York Times Magazine with text by Gideon Lewis-Kraus