Google sees all. This is o.k. because it uses this information to better serve ads that match your interest. It is not, however, a perfect system.
One of the problems with tracking search and other behavior to serve ads is that you will often need to look up information that actually has nothing to do with your purchasing intentions. You might be researching a topic for work, or looking at a location for a school project. That doesn’t mean you want to keep seeing ads for them since you are not going to buy the product or travel to the location. On top of that, after you do buy something Google rarely know this and so you continue to get bombarded with ads that are no longer useful.
Still, you’ve accepted that Google is tracking your every move, but that’s o.k. because you trust Google (mostly) and it serves a purpose most of the time – getting ads that you actually care about. And fortunately, you do have some control over the topics Google thinks you are interested. Go to “My Account”, and under “Personal info & Privacy” click on “Ads Settings”. Here you have some control over topics that you have been tagged with, and can even opt out of the whole program altogether. The down side is that you then go back to getting random ads that are not useful to you. One nice feature is that if you opt out, your whole topic history is deleted. If you then turn it back on again, you start with a clean slate.
But what about all the other ad serving companies out there? Google is not the only game in town, and unless you look closely at each page’s source code (or use tools to control ads), you don’t really know who is tracking you. For that you should check out the Digital Advertising Alliance Consumer Choice Page. There are 127 different companies participating in this organization and you will see which ones are currently tracking you. This includes Adobe, Google, Facebook, Amazon, and a raft of smaller ad companies you’ve never heard of. But they’ve heard of you! At least, they know your browser. The url to go there directly is http://www.aboutads.info/choices/ and you can specify which companies, if any, you want to opt out from. Note that these are only the companies that have voluntarily participated in this, but all the big ones are in there.
Great! Or so it seems, but one big caveat to remember is that this does not actually mean they will stop storing data on you (although for Google it does), it just means that they won’t serve ads based on that information. If you want privacy, get a blocker like Ghostery at https://www.ghostery.com/ .
Unfortunately cookies are not the only way to track you. There are other ways to fingerprint your computer besides cookies. Your browser, your system environment, even your graphics card behavior can be used to create fairly accurate fingerprints for each unique system. Not as good as a cookie (and really, what is, except maybe for cake?) but still pretty close. Using a system like Tor (https://www.torproject.org/ ) helps by blocking a lot of the information needed to accurately fingerprint you, but nothing is perfect.
Going beyond just browsing, there are lots of companies tracking what you do on their site. These are companies that offer a free service but make you log in to access it (Facebook, for starters). As the old saying goes, if you are not paying for something then you’re not the user, you’re the product. A site that offers you a free service or free information about much of anything – recipes, company data, whatever, is also tracking what you are looking at. If that company makes you log in to access the information, even if it is free, they know exactly who you are and what you are looking at. That might also be harmless but you do need to keep that in mind.
One more recent thing to watch out for are browser extensions., You can get browser extensions that provide extra information about the content of any web page. There are two things to consider here. First of all, most of these only offer a minimal amount of information and are really just ads for their full info. They will often give out a little actual information, tell you that they have more information, and give you a way to buy the extra data. That might be useful, but just keep in mind that it’s not really free information, it’s an ad.
What is far more disturbing is that many of these extensions give you extra information about all the web sites you visit. That means that they are tracking *EVERY* web site you visit. Every site. And most of them require you to log in to a free account to use the service. So they know who you are, and they know *EVERY* web site you visit, all day long. Let that sink in. That is a huge amount of private information that you are giving away. Make sure that the extension works on-demand only (so you have to tell it go fetch the info instead of it automatically presenting it) and if you are not sure, you should disable it when you are not using it. Better yet, just don’t use it.
So in the end, you are going to be tracked by a lot of different companies who are gathering a lot of information about you. In some cases, you have no choice if you want to use what the web has to offer. Google gives you search information, and they track your searches. Facebook lets you share information with friends, but they track you and make you log in. That’s the trade-off you have to make. Just make sure you make it knowingly and are aware of the data you are sharing with these different companies.