Those Ads That Follow You Around the Internet Are Ruining Christmas

Caroline Dohack found the perfect surprise Christmas gift for her husband on Amazon’s website this year: a hunting-grade slingshot and steel balls to protect their chickens from killer raccoons. “I was really pleased with myself,” said Ms. Dohack, 33, of Columbia, Mo.

On Saturday, the surprise unraveled. As Ms. Dohack tried to show her husband another gift she’d ordered on their shared Amazon account, the order history flashed on the screen.

“I was really disappointed because I wanted this to be a surprise, and I was anticipating him opening it and being excited,” she said. “At least those raccoons are going to be surprised.”

As more shoppers migrate from the mall to their phones, tablets and computers, Christmas surprises are getting harder to pull off. People with online accounts say they live in fear of having their covers blown by their browsing histories, or by increasingly sophisticated cookies that generate ads that follow them around the internet. Home package deliveries and tech-savvy children are compounding the problem, too.

“Before you used to check mom’s closet for all your presents, and now you check her online account,” said Kim Martin, 26, who shares an Amazon account with her parents and sister. Ms. Martin figured out she’ll be receiving the pair of TOMS slippers that were on her wish list because ads for them popped up on her mother’s Facebook page. “Oh, I guess I know what I’m getting now,” she joked with her mom.

Renee Gerkens said she knows her two older children peeked at her Amazon account. Her 12-year-old daughter approached her to say she preferred a different color of hairbands than the set already in Ms. Gerkens’s Amazon cart. Her 10-year-old son politely suggested she should consider looking for a drone, which wasn’t yet in her viewing history.

“They were totally critiquing all of my orders,” said Ms. Gerkens, 39, who works part time at a church. “I said, ‘Well great, you’re not getting anything. I’m deleting it all.’ Which I didn’t do, of course, because all my best ideas were in there.”

There are tactics to prevent such incidents—such as deleting cookies, turning off recommendations and creating separate accounts. Amazon said it encourages using its “Household” offering, which keeps the order histories secret on family accounts. It also recommends choosing the “gift” option at checkout, which should help prevent a shipment from arriving in its original packaging.

Some parents believe they can ward off Christmas snooping by assiduously guarding their passwords. It doesn’t always work.

While Bethany Howell napped on the couch last week, her daughter Ashlynd, 6 years old, used her mother’s thumb to unlock her phone and open the Amazon app. “Two hundred and fifty dollars later, she has shopped for all her Christmas presents on Amazon,” said Ms. Howell, of Little Rock, Ark.

After Ashlynd’s parents received 13 order confirmations for Pokémon items, they initially thought they’d been hacked, then they figured Ashlynd had bought them unintentionally. “No, Mommy, I was shopping,” Ms. Howell said her daughter told her. “But don’t worry—everything that I ordered is coming straight to the house.”  Ms. Howell added: ”She is really proud of herself.”

The Howells could only return four of the items. So Ms. Howell came up with a solution and told Ashlynd, “Well, Santa found out and that is what Santa is going to bring you for Christmas.”

Zeke Tischler, a 30-year-old social-media professional from Northridge, Calif., had the same sort of gift problem outside of the Christmas season. Ads for engagement rings began popping up in his Facebook news feed after he searched for rings online last year.

One evening, as his girlfriend was looking over his shoulder, an ad for opal engagement rings—her favorite gemstone—popped up on his Facebook news feed. Mr. Tischler said he tried to pass it off as a glitch.

Several weeks later, however, when he got down on one knee and presented the opal engagement ring, his girlfriend presented her own ring for him. Online ads ”ruined one of the largest surprises in my life,” Mr. Tischler said. His fiancée, he added, “thinks it’s pretty hilarious.”

A crush of package deliveries undid Brenna Jennings. Her United Parcel Service Inc. driver showed up so often to her New Hampshire home that her 8-year-old daughter started pondering the imponderable. Ms. Jennings shut it down with an explanation: Amazon and UPS are Santa’s helpers.

“I have to tell her that, yes, some of it is from the North Pole because Santa can’t fit everything on his sleigh,” said the 43-year-old website manager.

When Amazon sends gifts, some items come in their own boxes instead of Amazon’s brown packaging. That was how then-7-year-old Eric learned his family had ordered him an electric dirt bike and a Pogo stick when he answered the door for the delivery man last year. “I had to eventually make a no-answering-the-door rule, so he wouldn’t see what he was getting,” said his father, Jim Cooper, of Cary, N.C.

The flood of packages didn’t shake Eric’s beliefs. “It’s OK, Mama. I know that Santa Claus isn’t real,” Eric told his mom. “I know it doesn’t come from you guys either. I know it comes from Amazon.”

A lot more is coming from Amazon and its rivals this year. Online sales are forecast to grow nearly 10% this November and December from a year ago to as much as $117 billion, according to the National Retail Federation, accounting for roughly 18% of total holiday sales.

Magin Urdanick discovered another, unrelated downside to the digital Christmas revolution. Her 8-year-old daughter, Allie, wasn’t sure how to spell Santa’s name for a letter she was writing him. Ms. Urdanick made the regrettable suggestion that she ask Siri, Apple Inc.’s AI assistant.

Siri displayed the definition of Santa, which described him as an “imaginary figure.”

“My heart dropped,” said the 45-year-old real estate photographer. She scrambled to cover. “I said, ’Siri is so funny, she doesn’t know what she’s talking about.’ ”

When asked if Santa is real, Amazon’s Alexa AI assistant responds: “I don’t know him personally, but I’ve heard a lot of good things about Santa. If I ever meet him I’ll tell you!”

Siri is a little sassier. “Really. I’m surprised you have to ask,” she said.

—Jack Nicas contributed to this article