Why there's a white plastic ball in Guinness beer cans

• The Guinness widget is a tiny, plastic ball inside beer cans.
• During canning, pressurized nitrogen is added to the brew, which trickles into a hole in the widget.

Have you ever noticed the clink-clank of a tiny object rattling around the inside of an empty Guinness bottle or can?

That little gadget is called a widget, and you should be thankful for it. It's making your beer taste like it was just poured fresh from the tap.

How the Guinness widget works

A widget is a hollow, spherical piece of food-grade plastic with a tiny hole in it, Guinness representatives told Insider over email.

It basically looks like a little ping pong ball.

During the canning process, brewers add liquid nitrogen to the beer immediately before sealing it up. The liquid nitrogen quickly evaporates in the container. But since the can is sealed, this creates pressure inside it, which then forces gas and liquid into the widget through its tiny hole, per Guinness.

Then, when you open the can, you should hear a "pssshhh" sound. That's the gas and liquid leaving the widget, which mixes with the beer, creating that foamy head so iconic in a Guinness draft, Guinness said.

For canned Guinness, you should pour the beer into a glass after opening, but the bottle widget (which is shaped like a rocket) is designed for you to enjoy the beer straight from the bottle.

Guinness released its first-generation widget in 1989

Guinness brewers first patented the idea of the widget in 1969. But it wasn't until 1989 when they released their first-generation widget, Popular Science reported.

This first-generation widget was a flattened disc that sat at the bottom of the can. It did its job well when serving the beer cold, but if the beer was warm, it could overflow after the can was cracked open, per Cool Material.

In 1997, Guinness released the floating, spherical widget you can find in cans today — which they call the "smoothifier" — to fix this problem.

Carbon dioxide vs. nitrogen in beer

Breweries typically use carbon dioxide to give a beer its quintessential bitter fizz, but when a drink calls for a sweeter, silkier experience — like when drinking a Guinness — brewers infuse the ale with nitrogen rather than with carbon dioxide.

In fact, Guinness was the world's first nitro beer. Nitrogen bubbles are smaller than CO2 bubbles, so the resulting head and taste is smoother and more delicate.

Fergal Murray, a Head Brewer at Dublin City Brewing Co., told Forbes that there are 300 million bubbles in a pint of Guinness compared to the up to 2 million bubbles in a typical lager.

Also because nitrogen bubbles are smaller, they're more stable. Therefore, when you crack open a beer, more of the tiny bubbles will stay intact. This — along with the smaller bubbles — gives the brew a thicker, more velvety "mouthfeel" without the acidic bite of carbonation with CO2, per Home Brew Advice.

Because of the fleeting nature of nitrogen gas in liquid, it's hard to maintain tasty levels of the gas in packaged beers once you open them. That's where Guinness' widget comes into play, because of how it's able to slowly release nitrogen into the beer upon opening.

The popularity of widgets have caught on since Guinness introduced them in the late '80s. Other beers, such as Young's Double Chocolate Stout, Murphy's Stout, and Boddingtons Pub Ale, all have widgets in their cans.