‘It’s a little known fact . . .” everyone’s favorite know-it-all, Cliff Clavin, would often say on the show “Cheers.” The sentence would end with something that is demonstrably not a fact — that beer makes you smarter, that tanning was invented in the Bronze Age or that everyone in the Swiss Army owns a Swiss Army knife.

What used to be a lovable doofus pontificating in a bar has spread way beyond that. We’ve become a country of know-it-alls, convinced that having all the information at our fingertips means we’re knowledgeable. “I can Google it” has become synonymous with “I understand it.”

We’ve become extremely annoying.

In his book “The Death of Expertise,” Tom Nichols addresses what he calls “attacks on established knowledge.”

He writes, “I fear we are witnessing the death of the ideal of expertise itself, a Google-fueled, Wikipedia-based, blog-sodden collapse of any division between professionals and lay-people, students and teachers, knowers and wonderers — in other words, between those with any achievement in an area and those with none at all.”

Anyone who has spent any time online has seen this in action. Crazed people take to Internet mommy forums to assert with unearned authority that believing the scientific community on life-or-death topics like immunizing your children is silly. “Do your own research!” they implore.

By that they don’t mean go to school for a decade, establish a lab, spend years studying viruses and then conduct scientifically rigorous tests. No, they mean choose your own conclusion, Google a phrase that sums it up (like “vaccines cause autism”) and reverse-engineer a conspiracy rant masquerading as an argument.

Be an Internet troll, in other words. Like them.

While people like that take their know-it-allness way too far, many of us are guilty of being a kind of modern know-it-all.

Here are some easy ways to tell if you’re falling into the trap:

You consider yourself an expert on something because you’ve perused the subject’s Wikipedia page or you decide you’re able to diagnose illnesses because you’ve visited WebMD. Wikipedia can be a valuable resource as a collection of footnotes that can be at least checked for accuracy instead of merely asserting a bunch of “facts,” but it isn’t a replacement for a book or five on a subject. And it’s certainly no replacement for years of formal study. Similarly, WebMD may be useful late at night to rule out serious conditions when you have the sniffles, but it’s not in the same universe as actually being a medical doctor. Yet too often people treat their casual scrolling of WebMD or Wikipedia as enough of an education on a subject to instruct others. There’s a reason doctors hate when patients refer to WebMD when describing their symptoms. You’re not a doctor, so stop playing one on the Internet.

You think you know more than your friends . . . about everything. Either you have really dumb friends or you’re not as smart as you think. If you start too many sentences with “Actually . . .” you might be the annoying know-it-all in your group of friends.

You’ve said “learn some history” or “learn some science” when you yourself weren’t completely sure you knew the history or understood the science. This is one of the worst ways that this know-it-allism manifests itself. It’s bad that people pretend to know everything, but mocking other people for not pretending too is where it becomes peak irritating.

You’re willing to talk on any subject at any time, especially if you once caught a late-night documentary about it. Your late-night viewing of the Civil War documentary doesn’t actually make you a Civil War expert, so should you encounter an actual Civil War expert, defer to them.

You offer advice on subjects you don’t really understand to people who haven’t asked. Did you read an article on housing prices and now feel qualified to offer real-estate tips to friends? Did you catch a business news announcement on a TV scroll and now are telling people to buy a stock? Stop it.

It’s OK to not know everything and to admit that sometimes. We’re not meant to be experts in everything, and it doesn’t make a lot of sense to try. Expertise is something developed over time and through study, not picked up in passing to impress friends.

Little known fact: They’ll be more impressed if you talk about things you actually understand.