“Anyone can edit Wikipedia,” the adage goes. But, it turns out, a relatively small number actually do.

What is worthy of a digital page in the world’s largest and most-read encyclopedia is decided by roughly 270,000 active volunteers, enthusiasts who populate the online resource with information on anything from 19th-century medicine to TikTok trends. Inevitably, some subjects are sidelined – the global south, notable women – but a new batch of Wikipedian recruits are waging war on one neglected topic: the arms industry.

Last week, in a classroom in central London, two dozen volunteers huddled around laptops and free servings of vegan Ethiopian food for what is known as a “wikithon”, an event of collective and in-person Wikipedia editing. Some were veteran editors in their 70s, others young students who had never registered an account before. But their targets include subjects such as Palantir, Project Maven and Nitro-Chem.

“Wikipedia pages about the arms industry, in general, are not always super-detailed,” said the group’s co-founder Agnes Cameron. The intention of the wikithon, started by fellows from the n-Space programme at Somerset House Studios, was “to put better quality and more well organised information on the arms industry in the public domain”, the specialist technician said.

Attenders at the monthly event are trained in how to add to the internet’s most popular reference site. But while editing Wikipedia is surprisingly simple – just a few clicks to publish a change – ethical complications quickly bubble up.

“The interesting thing about Wikipedia editing is that you’re encouraged to edit things you care about,” Cameron said. “What it looks like to have a conflict of interest is an interesting question.”

Although Cameron enjoys editing pages about food in her spare time, her interests are also political. “We’re toeing quite a difficult line,” she said. “Difficult lines are important to toe.”

Despite personal and political reasons for wanting to spread information on arms manufacturers and sellers, finding journalistic balance means using Wikipedia in good faith. Cameron said attenders’ chosen subject matter meant that it was “really important” that they followed Wikipedia’s standards to the letter. “This is not an anti-arms industry campaigning event. This is an event really about factual information on Wikipedia,” she said.

When it comes to information, Wikipedia’s rules demand that no original research is included on its pages and conclusions are not drawn. The main goal of the arms industry wikithon, then, was to pull together publicly available information from other sources into one place.

Wikipedia has been repeatedly criticised for its lack of diversity in editors and its coverage. It has been accused of geographical bias towards the west, with most articles focused on the US and western Europe. Similarly, just 19% of the site’s biography entries are for women. In 2018, the female Nobel prize winner Donna Strickland, a physicist, was deemed “not important enough” for a Wikipedia entry.

With a wider range of ages, genders and racial backgrounds at the wikithon, the trainee editors were helping to rebalance the scale, said Hannah Cobb, a co-founder of the event. “There’s a very specific idea of who edits Wikipedia … that doesn’t tend to be the demographic of who shows up,” she said. “There’s a really broad interest in Wikipedia in general. Everyone remembers that at school you were taught not to trust it because anyone could write it.”

Previous arms industry wikithons organised by Cameron and Cobb in Manchester and London have drawn in more than 60 would-be Wikipedians at a time, including activists, journalists, Quaker members – and even Cameron’s own mother.

Newcomers to the group were interested in how Wikipedia could be used to broaden public knowledge of confusing geopolitics, said Cobb. “There is a sense of powerlessness when it comes to countering the narrative by big tech, by governments, by the military industrial complex at large,” she said.

But for the arms industry page editors, those feelings can disappear over a few hours: “When you write something on Wikipedia, it appears immediately on the internet. I think that experience alone is quite empowering for people.”

Cobb spoke of a sense of wonder “when people realise how easy it is to actually contribute”, but attenders have a respect for Wikipedia’s commitment to rigour and quality control. And though dedicated to accuracy, the group prefers to not advertise the details of its edits over concerns that the work could be undone by other editors in bad faith.

Cameron said it was unclear if Wikipedia’s wider editorial culture would take offence over how the event was run. While wikithons are not new, the blurry line between activism and accurate dissemination of information stress-tests the platform’s rules.

Real-world politics often spill on to Wikipedia, and editors often disagree publicly about changes. The site has also been covertly used as an informational battleground. The seasoned editor Ksenia Coffman made extensive edits to remove what she found to be flattering and sympathetic entries about Nazi party officials across Wikipedia, and in 2021, the Croatian-language version of Wikipedia was found to have been commandeered by nationalist, far-right organisers who made ideologically motivated edits.

Cameron hopes that the regular meetings can be formalised into a WikiProject, when organised groups of editors collaborate to improve certain topic pages. She hoped her group could be adopted by WikiProject Military history, which she called “far and away the most active project on Wikipedia by miles. It’s amazingly well run.”

The London wikithon is to continue for another session in the winter, and Cameron and Cobb’s faith in encyclopedia editing as a political tool is steadfast. As Cameron said: “Wikipedia is fundamentally anti-fascist.”