In addition to writing for this blog, I spend a lot of time writing for the advertising world, particularly online advertising. That means I’ve probably unintentionally helped creep you out before as you surf the web, thanks to an advertising practice known as retargeting.

Even though retargeting is extremely common in online advertising, this particular danger was recently discussed at AdAge, it seemed like something that those outside the advertising industry should know about.

We’re Not Trying to Be Scrooges

Here’s how retargeting works. You visit a website to learn about a product, but you don’t buy it. Google keeps track of the sites you visit, and often shares that information with advertisers who are eager to sell you the items you search for. Now we know the exact items you’re interested in, which means we can make the ads on all the sites you visit more relevant. So in case you weren’t aware, no, it’s not a coincidence when you see ads for products you were just looking at.

Retargeting is in advertisers’ best interests, and advertisers like to think it helps you, too. But what if the holiday gift items you’ve been shopping for appear repeatedly in ads when your family uses your shared computer? They may get wise to you. Sorry about that.

We’re Not the Only Ones to Blame

In addition to the advertising problem, most browsers also now offer auto complete and history features, which can give away the sites you visit. The more frequently you visit those sites, the more likely the browser is to suggest them. So when your loved one types “T” to go to The Local Paper’s website, your browser may just reveal that you’ve been spending time on Tiffany’s site.

What You Can Do About It

Fortunately, there are a couple easy ways to preserve your holiday surprises. The first is to do all your gift-related searching using your browser’s privacy mode. Doing so will make all the sites you visit during that session invisible to anyone else using that computer. Here’s an example of how it works in Firefox, though every browser now offers a similar feature.

You can also enable ad-blocking software — and I feel like a traitor for even suggesting it. Clearly, the ads I write are relevant to your interests, and you should never ignore them. That said, ad blockers are typically browser add-ons that you can download, and they make ads show up as blank space. Ad blockers can affect some site functionality to a small extent, so keep that in mind. Another trick is to adjust your browser’s preferences to limit or eliminate sites’ use of cookies and tracking.

It’s Probably Not Too Late

If you forgot to enable privacy mode, you can go back and clear your recent browser history after your shopping is done. But that leaves a sort of trail, as auto-complete won’t work at all, and users will have to re-enter passwords on sites they frequent. And that can look suspicious to the tech-savvy, so if you get called on it, just tell the truth: “Honey, Chrome/Firefox/Internet Explorer/Safari wanted to spoil your Christmas. Can’t let that happen.”

What’s On My Wish List

No one likes ads, but if anything you’ve read here helps you out during the holidays, do me a solid and just click on one ad, any ad, and we’ll call it even.

Something that should be on everyone’s wish list is a faster Internet connection. No matter how hard someone is to shop for, shopping gets a little easier when it gets a little faster.

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Image by Daniel Foster/Flickr