Online advertising techniques explained

It’s hard to go anywhere on the internet without seeing an ad. That’s because advertising is the predominant business model of the internet today. Websites and apps you visit every day are largely “free” for you because they monetize your data and your attention through advertising. And, as data sets of individuals and groups online have become more readily available to companies in recent years, advertisers have developed strategies to minimize what they spend on ads while maximizing the profit made from them. The ad tech arms race is constantly evolving, and the more invasive practices that are used, the more valuable your data is. Here are some of the most common online advertising strategies and associated activities being used that rely on collecting data about you today.

Targeted advertising

Targeted advertising is when you are shown an advertisement based on something specific an advertiser thinks they know about you. Advertising technology providers have become adept at creating profiles about you based on what you see, read and click on online (and sometimes what you do offline, too – like what you purchase with your credit card). Advertisers use these profiles to serve you with ads that they think you’re more likely to engage with than others. Targeted advertising is often used by companies so that their dollars aren’t wasted on consumers who won’t find their product or service valuable. Some people enjoy receiving targeted ads because they may be relevant; others feel uneasy about receiving targeted ads due to the fact that their information has been collected and shared by companies they’re not aware of.

Targeted advertising is an umbrella term that encompasses many of the more specific strategies that follow in this article (like retargeting, contextual advertising, cross device tracking, browser and device fingerprinting, and behavioral profiling).


In planning for your friend’s bachelorette party, you search Amazon for decor to make your friend’s weekend special. In the weeks that follow, Amazon serves you ads on other sites showcasing products commonly bought for bachelorette parties that you might be interested in. Amazon could have used a range of targeted advertising strategies to do this, such as retargeting, cross-device tracking, or behavioral profiling.

Targeted Advertising: Amazon Ad


Ever feel like an ad is following you around online? It probably is, and this is the result of retargeting. Retargeting happens when a cookie hitches a ride with you from one website to another, or when a company tracks your logins or device IDs from one time and place to the next.


You casually browse through Redfin to see what real estate listings are available in your area. You then log into Facebook to scroll through your timeline and catch up with friends. Lo and behold, there’s a Redfin ad in Facebook’s right hand column. Redfin was able to show you an ad, retargeted to you after you left their platform.

Retargeting: Redfin Ad

Contextual advertising

Contextual advertising is when you’re shown an ad based on the content of the website you’re on. Reading an article about sports? If you’re shown an ad for a sporting goods store while you’re on the page, it’s plausible that the advertiser didn’t use personal data at all to get their ad to you, but instead simply relied on the content of the page itself to suggest whether or not you might be interested.


Your New Year’s resolution is to swim more. You read an article on about the benefits of swimming to motivate yourself. In the right hand column, you see an ad for CoolSculpting, which may be contextually advertised to you based on the content of the article you’re reading and nothing more.

Contextual Advertising: CoolSculpting Ad

Cross-device tracking

Cross-device tracking enables ad tech companies (including Google, Facebook, and data brokers that sell your information to advertisers) to track you across multiple devices such as smartphones, television sets, tablets and computers. These companies can use your identity (e.g., your login information), the fact that your devices all use the same home network, or even ultrasonic signals to create your data profile across more than one device. For example, one such form of this tracking uses audio beacons, or inaudible sounds, emitted by one device and recognized through the microphone of the other device.


You research 5G in your computer browser because you want to better understand both the skepticism and also the potential of the technology, and you read several articles on news websites to get perspective. Later that day, when you log into your New York Times app on your phone to read through today’s top stories, you see a Verizon ad about their 5G products. How did the news app and advertiser find you on your phone if you were only browsing for 5G information on your desktop? Cross-device tracking could be the culprit.

Cross-device Tracking: Verizon Ad

Browser and device fingerprinting

Fingerprinting is used to identify you through your browser or device, based on their specific and unique configurations. Fingerprinting technology was initially developed with good reason: to help make your browsing experience better. For example, fingerprinting has historically helped with online image rendering across different devices. Today, fingerprinting is highly attractive to advertisers because it’s possible to collect information about you and target you with advertising, even if you browse with tracking protection or regularly clear your cookies. This makes fingerprinting one of the most invasive strategies for advertising.


Recently, Geoffrey A. Fowler of The Washington Post wrote an expose on online fingerprinting. In his piece (republished here in the Denver Post without a paywall), he asserts that fingerprinting is happening on sites you wouldn’t think would be intrusive, like So maybe that’s why you saw that Williams Sonoma cookware ad there last week (as someone who recently researched Instant Pots while being vigilant about your privacy settings while you did so).

Browser Fingerprinting: Williams Sonoma Ad

Behavioral profiling

Behavioral profiling is a specific kind of tracking that records, measures and analyzes information about the specific things you do on a website or across multiple websites. The idea is to gain information about the kinds of activities you do, interests you have, the way that you act and the way that you react. For example, an advertiser using behavioral profiling might try to determine whether you are an “impulse buyer” or a “sale seeker”. This kind of profiling can be used to give you recommendations about products and services that you might be interested in. However, it may also potentially exclude you from offers or content based on your behavioral profile.


Your fur-baby is your first-born and your best friend. You generally spare no expense when it comes to buying your pup the perfect food to fit her dietary needs, or that festive bandana for the upcoming holiday. Your data profile online might suggest that you love dogs and that you are happy to spend a sizable portion of your disposable income on them. Hence why you receive a Furbo Dog Camera ad on Instagram, which could have used behavioral targeting to reach you.

Behavioral Profiling: Furbo Dog Camera Ad

Dynamic pricing

Dynamic pricing is the practice of pricing items at a level determined by your perceived ability to pay. Dynamic pricing algorithms can target you and profile you based on the data that they have about you, such as your location, search and purchase history, the number of times you’ve visited a site, and the device you are using. Dynamic pricing itself isn’t an advertisement or an advertising strategy, but it’s often used in complement to advertisements in order to prompt purchasing behavior.


You’ve been researching flights from Washington, DC to Hartford, CT, and today when you log in, you see that the price has gone up to $1,080 for roundtrip fare. The cost may seem outlandish, but American Airlines has deemed you and others able to afford — and be willing to pay for — this ticket. American Airlines conveniently places a booking button right in the Google Flights interface.

Dynamic Pricing: American Airlines Ad

Data brokering

A data broker is often an important intermediary to executing advertising strategies that rely on the use of your data. A data broker collects information about individuals from public records and private sources. The data they collect is combined through efforts like data matching (finding data about you from multiple sources and linking them) and audience matching (building your profile based on ‘lookalikes’ – people who behave similarly to you online). Through these efforts and others, data brokers are able to create profiles of you, often made up of thousands of individual pieces of information. Data brokers sell the information they collect about you to companies and government agencies to make their profit.


Large data brokers include Acxiom, Experian, Epsilon, CoreLogic, Datalogix, Intelius, PeekYou, Exactis and Recorded Future.

You can reduce what advertisers know about you

Advertising isn’t going away anytime soon, and it probably shouldn’t, as it supports publishers and content creators. And, many of the things that enable advertisers to track you (like cookies) are likely here to stay too. At their best, they make your life easier by storing information and improving your web experience. At their worst, they exploit your vulnerabilities and take advantage of very personal information. But, you do have the power to limit what advertisers know about you. Here are five easy ways:

  1. Use technology that respects your privacy. The Firefox browser blocks trackers by default — over 10 billion every day — so more of what you search for and click on is unavailable for the types of advertising and tracking in this article. And, Firefox automatically blocks known fingerprinters, so when you use Firefox, you reduce your individual profile for advertisers based on your laptop, phone, software, add-ons and preferences. Here’s where you can download the Firefox browser. 
  2. Use an ad blocker. Ad blockers prevent ads from displaying in your browser. Because you see and interact with less ads while using an ad blocker, data brokers and the companies they serve collect less data about you. Here’s a curated list of ad blocker extensions that have been reviewed by Firefox’s security team as safe. 
  3. Avoid signing into websites and apps through Facebook or Google. Instead, create unique usernames and passwords.
  4. Limit the apps on your phone to the essentials. There are thousands of apps out there that maintain their existence by sucking up your data and selling it to third parties. The buying and selling of location data, for example, is big business and can be quite invasive, especially when it’s combined with other data about you.
  5. Turn off mic access on your computer and phone. Deactivate “Hey Siri” or “Okay Google” and disable mic access for your phone apps. Head over to System Preferences on your Mac or PC to turn off mic access as well.

A note about Firefox advertising

You might have seen a Firefox advertisement in an email from the New York Times. Or, maybe you’ve heard a Firefox promotion on a podcast you enjoy, like Judge John Hodgman or Wait, Wait, Don’t Tell Me.  Firefox does indeed advertise, and we do it with integrity. We put your privacy first and foremost, from the products we make to the marketing campaigns we run. Advertising strategies like site retargeting, third party or non-consensual cross-device tracking, device and browser fingerprinting, and the use of data brokers are things we don’t do. Our focus is and has always been people over profit.

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