Romain Degrave first discovered Omegle three years ago, when he was still in high school. Since its inception in 2009, the online service, which randomly pairs strangers for anonymous video chat sessions, had been connecting users across the globe for moments of discovery, whimsy, cross-cultural exchange and political debate.

The delight of Omegle was in its randomization: with the click of a button, at any moment, you could be connected with a complete stranger while in the comfort and safety of your own home, and — unlike with a conversation in the real world — you had the option of ending that encounter at any time, the second it got boring or uncomfortable or weird. On Omegle, you could meet a new best friend, the love of your life or a skilled debater who could effectively challenge your misconceptions and assumptions.

Unfortunately, this randomization meant users could also be connected with more dangerous people, even sexual predators — a scourge all the content moderators in the world couldn’t entirely eradicate or protect users from.

That’s one of the reasons Omegle’s owner, a Vermonter named Leif K-Brooks, abruptly decided to shutter the service on Thursday, after nearly 15 years of operation. In his farewell note, Mr. K-Brooks, who created Omegle when he was 18 years old, acknowledged that the service had become a haven for criminal activity, but also issued a call to arms, to stop what he sees as the toxic trajectory of today’s internet.