Some brands are 'slack-filling' to cleverly disguise how much product you actually get

• Slack-fill describes the empty space in a packet, such as the air in a bag of potato chips.
• Slack-fill can be deemed illegal if it's not functional.
• Halo Top, Mondelez, and Whole Foods have all been unsuccessfully sued over slack-filling.

Ever opened a bag of potato chips, only to find that it's half full of air?

There's a name for that empty part of the packaging: slack-fill. You can find it in products from packs of cookies and noodles to bottles of laundry detergent and even makeup, and consumer advocates say in some cases be used to sneakily deceive shoppers.

Slack-filling isn't illegal in essence. The FDA – which defines slack-fill as the "difference between the actual capacity of a container and the volume of product contained therein" – says that sometimes slack-fill can be functional, making it legal.

For example, slack-fill is needed to protect the container's contents or to ensure the packaging is big enough to accommodate required food labeling. Sometimes it's unavoidable during manufacturing.

However, slack-fill can also lack any function, so if customers can't see the contents before purchasing, then it could be considered misleading, the FDA says.

"We buy with our eyes – we're influenced by the size of the package," Ed Dworsky, who runs the consumer-advocacy website Consumer World, told Insider. When people see large packages, the "natural inclination" is to believe it has a large number of contents, too, he said.

Dworsky suggested that some brands used slack-fill to deliberately mislead shoppers into thinking they're getting more product than they really are. Another sneaky tactic is shrinkflation – quietly reducing the amount of product but keeping prices the same.

New York law firm Patterson Belknap said in 2019 that "after decades of FDA non-enforcement, slack-fill has recently risen to prominence due to the efforts of enterprising plaintiffs' lawyers." The firm noted that these lawsuits are generally dismissed, in part because it's hard to prove that slack fill is nonfunctional.

Disgruntled customers are still filing lawsuits nevertheless. One class-action suit, filed in June in the Northern District of California, alleges that Whole Foods sells its 365: own-brand macaroni and cheese products "in oversized, opaque boxes that do not reasonably inform consumers that they are half-empty."

The judge dismissed many parts of the case earlier this year, including its class-action status, and said that a reasonable consumer would not be deceived by the products.

Another class-action complaint, filed in January 2022 in the Northern District of Illinois, made similar allegations about some packs of Whole Foods 365 pilaf rice sold in cardboard boxes. Whole Foods argued that the packaging wasn't deceptive because it stated the product's weight. In August, the judge dismissed the complaint.

Halo Top and Mondelez have been unsuccessfully sued over slack-fill, too, lawsuits viewed by Insider show.

In response to the lawsuits filed against them, companies generally argue that their packaging follows federal slack-fill regulations, features the weight of the products, and has to be that size to accommodate settling during transport.

But slack-fill lawsuits aren't always dismissed. 

In 2019 California prosecutors reached a $750,000 settlement with chocolate brands Ghirardelli and Russell Stover, both owned by Lindt & Sprüngli, over accusations that some of their products were packaged in oversized containers that disguised how many chocolates customers were actually getting.

The brands didn't admit to wrongdoing. Part of the settlement involved changing the packaging to add a transparent window.

While there isn't evidence to suggest that nonfunctional slack fill is on the rise, it could be something consumers keep a closer eye on as they look to get the most value for their buck amid soaring inflation.