FUELLED by curiosity, coding know-how and caffeine, “hackathons” have been a pastime for tech geeks for a decade. In lengthy sessions often stretching through the night, software engineers fix bugs and come up with new ideas. Facebook’s “like” button was born during such a late-night coding session.

However, hackathons are no longer the exclusive domain of techies. Several hundred big companies in other industries now have them, reckons Rob Spectre of Twilio, a software firm, up from only a handful two years ago. These include firms in industries as diverse as airlines, cars, telecoms, beer and banking.

Last month a group of British railway companies held a 48-hour session on board a train. One of the teams came up with a way to scan carriages and alert passengers to where they might find vacant seats. On December 5th-6th MasterCard, a credit-card processor, is holding its 13th hackathon of 2015: a season finale, of sorts, following a dozen regional “championships” around the world.

Hackathons differ in their scope, but most require participants to devise a solution to a problem within a day or two; the winning team is typically awarded some sort of prize. Though the ideas are off-the-cuff, they can sometimes be impressively original. Some hackathons are internal events, which offer employees the opportunity to work with new teams and to broaden their experience. Every year Dropbox, a cloud-storage company, hosts a “hack week” when employees can work on any project they like. Disney, a media firm, holds four internal hackathons a year.

The majority of hackathons, however, are external events aimed at enhancing a firm’s reputation in the eyes of software developers. Some firms consider hackathons essentially as good PR, and pay for them out of their marketing budgets. Others find them helpful with recruiting. Hackathons reveal which participants can focus and perform under pressure, which is a good way to identify talent, says Sebastien Taveau of MasterCard.

Hackathons held by universities have become loaded with corporate sponsors, eager to reach young coders. “Job fairs no longer have any significance” for engineers, says Jerry Filipiak of Comarch, a software firm. “The hackathon has become the job fair.” To disguise their corporate agenda, the representatives of the sponsoring firms often call themselves “developer evangelists”.

As hackathons go mainstream, they are evolving to accommodate a wider audience. Some firms are experimenting with holding shorter gatherings, providing healthier food and offering child care so as to attract more female participants, says Susan Danziger of Ziggeo, a video-software firm. Purists will doubtless scoff that hackathons are abandoning their nerdy roots, but others are more open-minded. What’s wrong, after all, with hacking the hackathon?