For the next few weeks, whenever you do a work-related search or visit a work-related site, you see advertisements for tropical resorts, exotic hotels, and up-market tour operators.
What you are seeing are so-called "interest-based ads". They are ads served by Google, based on what Google knows about you. And you might be surprised at just how much Google does know about you. As well as your geographic location, Google knows about the things you're interested in (based on your search history and the types of sites you visit), where you hang out in social media, what mobile devices you use and where you use them, and quite a lot more. It also makes a good guess at your age, sex, marital status, and even your family income. It uses all that information to decide what ads to show.
You might not care about this. It might not matter to you that Google uses your personal information to send you targeted ads in this way. if so, that's fine.
On the other hand, you might find the whole thing somewhat intrusive. You might not want to see ads related to your leisure activities while you're at work - or ads related to your work while you're trying to relax. You might be worried if ads suddenly start appearing for the surprise present you've bought your spouse - or the medical condition you'd rather keep to yourself.
If so, you'll be pleased to know that you can opt out of seeing interest-based ads. Doing so doesn't stop Google collecting your personal information, but it does prevent them for using that information to decide what ads to show you. If that's what you want, follow these steps:
- Visit Google's Opt Out page.
- Scroll down to the section headed "How to opt out".
- To opt out of interest-based ads in Google search results and Gmail, click the first of the links below that heading. On the resulting page, click the blue Opt Out button (see screen shot, above).
- To opt out of interest-based ads on the websites you visit (what Google calls its "display network"), click the second link under "How to opt out". Again, click the Opt Out button on the resulting page.
You can reverse the process at any time. To do so, follow the same links, but this time click on the Opt In button.
Keep in mind that your decision to opt out is stored in a cookie in the browser you are currently using. That means that it won't apply when you use a different browser or a different computer. In that case, you will have to opt out separately for each browser and machine.
It also means that your setting will be lost if the cookie gets cleared for any reason. You can safeguard against that by installing a browser extension known as Protect My Choices. But you'll probably find it easier simply to go through the opt out procedure again.
If you're an AdSense publisher, you might like to know that you can prevent interest-based ads from appearing on your own sites. I explain how to do that in a separate blog post.