If you want a modern wonder of the internet, look no further than Wikipedia, which turns 15 years old today. It is gigantic (more than five million articles in English alone), and gigantically useful for those seeking a grounding in any topic. It has illustrated how the internet and the power of the crowd can disrupt established businesses: both the book-based Encyclopaedia Britannica and Microsoft’s CD-based Encarta fell before the onslaught of a simple collaborative document that anyone could edit and enhance. Even Google failed with its rival, launched in 2008 and killed amid indifference in 2012. I realised how much power the site had during a chat in 2008 with Larry Page, Google’s co-founder, who languidly said that he had followed the news of the Georgia invasion by watching the Wikipedia page about it. Why? Because it was factual, updated quickly, and did not use that annoying newspaper style of trying to make stuff sensational. Wikipedia, the news source? Sounds crazy, until you hear about people checking there on hearing that someone famous has died, to see whether it is really true. These days, you are not dead until you are dead on Wikipedia. Like Google, Wikipedia is a child of the internet; it insists that the web is the only source of reliable information. If a claim in an article is not supported by a factual link somewhere else on the web, the site’s always-watchful editors will delete it. Television and radio claims do not matter, do not exist; Wikipedia’s only reality is online. It even has a creation myth; people think it was the effort of Jimmy Wales alone, but in fact he and Larry Sanger (an “internet project developer” — thanks, Wikipedia) were working on the idea of an online encyclopedia called Nupedia, which began in 1999. That had expert writers and editors who would check their articles. As you can imagine, it was grindingly slow compared to Wikipedia, which offered the radical concept that anyone could write, and anyone could edit. Nupedia added 12 articles in its first year; Wikipedia, 18,000, starting from the first one, about William Alston (a Syracuse University philosophy professor then said to be “arguably the greatest epistemologist of the 20th century”). From Alston, Wikipedia exploded in size. The basic assumption that anyone could write or edit swept away the barriers that had existed to “publishing”. The bad articles attracted better editors, and they drew in better writers, and miraculously a virtuous circle kicked in. In December 2005, the science magazine Nature put Wikipedia up against Britannica for accuracy: it declared a tie. In its dying throes, Britannica tried to copy Wikipedia. It did not help: one cost money, the other was free. The success was helped by two other good decisions. First, Wikipedia aims for a “neutral point of view”, which has helped it evade most (if not all) controversy. Second, it eschews the advertising-based model that plagues other American efforts; calls for donations may grate, but an ad-free Wikipedia is the best of all possible worlds. That is not to say it is without faults. There are plenty, some deeply ingrained. Most of its editors are male, meaning topics relevant to women are underrepresented. As the site (and each editor) ages, it becomes harder to attract new editors as the existing clique becomes embedded. With no overall editor determining its direction or content, the topics and content can vary enormously. The world probably does not need zillions of explanatory articles about the Japanese video game franchise Pokemon – but perhaps could do with some of the articles about less-simple concepts being rewritten to a more novice-friendly standard. That is what the Encyclopaedia Britannica had that Wikipedia does not: consistency. But that is also the web revealing our real character. Those who can be bothered to create are more interested in Pokemon than explaining maths or science. We peer into Wikipedia, and see ourselves peering back. Because a Wikipedia page is almost always the top search result for any factual topic, it has become the substrate for our online knowledge. Will that remain true, though? As upcoming generations move to mobile, they are spending more time inside apps; and while mobile visits to Wikipedia have grown fast (they are just under 40 percent of visits), more time is spent in Facebook and other social networks, where misinformation can run rampant. At least Wikipedia tries to remain neutral. Here’s to the next 15 years. A version of this article appeared in The Telegraph on January 15, 2016