 Every day, billions of people come here with questions about all kinds of things. Sometimes we even get questions about Google search itself, like how this whole thing actually works. And while this is a subject entire books have been written about, there's a good chance you're in the market for something a little more concise. So let's say it's getting close to dinner and you want a recipe for lasagna. You've probably seen this before, but let's go a little deeper. Since the beginning, back when the homepage looked like this, Google has been continuously mapping the web, hundreds of billions of pages, to create something called an index. Think of it as the giant library we look through whenever you do a search for lasagna or anything else. Now, the word lasagna shows up a lot on the web, pages about the history of lasagna, articles by scientists whose last name happened to be lasagna, stuff other people might be looking for. But if you're hungry, randomly clicking through millions of links is no fun. This is where Google's ranking algorithms come into play. First, they try to understand what you're looking for, so they can be helpful even if you don't know exactly the right words to use or if your spelling is a little off. Then they sift through millions of possible matches in the index and automatically assemble a page that tries to put the most relevant information up top for you to choose from. Okay, now we have some results. But how did the algorithms actually decide what made it onto the first page? There are hundreds of factors that go into ranking search results, so let's talk about a few of them. You may already know that pages containing the words you search for are more likely to end up at the top. No surprise there. But the location of those words, like in the page's title or in an image's caption, those are factors too. There's a lot more to ranking than just words. Back when Google got started, we looked at how pages link to each other to better understand what pages were about and how important and trustworthy they seemed. Today, linking is still an important factor. Another factor is location, where a search happens. Because if you happen to be in Orimea, Italy, you might be looking for information about their annual lasagna festival. But if you're in Omaha, Nebraska, you probably aren't. When a webpage was uploaded is an important factor too. Pages published more recently often have more accurate information, especially in the case of a rapidly developing news story. Of course, not every site on the web is trying to be helpful. Just like with robocalls on your phone or spam in your email, there are a lot of sites that only exist to scam. And every day, scammers upload millions more of them. So just because InstantVirusDownload.net lists the words lasagna recipe 400 times, that doesn't mean it's going to help you make dinner. We spend a lot of time trying to stay one step ahead of tricks like these, making sure our algorithms can recognize scam sites, and flag them before they make it to your search results page. So let's review. Billions of times a day, whenever someone searches for a lasagna or resume writing tips or how to swaddle a baby or anything else, Google's software locates all the potentially relevant results on the web, removes all the spam, and ranks them based on hundreds of factors like keywords, links, location, and freshness. Okay, good time to take a breath. This last part is about how we make changes to search and it's important. Since 1998, when Google went online, people seem to have found our results pretty helpful. But the web is always changing and people are always searching for new things. In fact, one in every seven searches is for something that's never been typed into the search box before, by anyone ever. So we're always working in updates to search, thousands every year, which brings up a big question. How do we decide whether a change is making search more helpful? Well, one of the ways we evaluate potential updates to search is by asking people like you. Every day, thousands of search quality raters look at samples of search results side by side, then give feedback about the relevance and reliability of the information. To make sure those evaluations are consistent, the raters follow a list of search quality evaluator guidelines. Think of them as our publicly available guide to what makes a good result good. Oh, and one last thing to remember. We use responses from raters to evaluate changes, but they don't directly impact how search results are ranked. So there you have it. Every time you click search, our algorithms are analyzing the meaning of the words in your search, matching them to the content on the web, understanding what content is most likely to be helpful and reliable, and then automatically putting it all together in a neatly organized page designed to get you the info you need. All in, oh, .81 seconds? Wow, anyone else ready for dinner? Interested in learning more? We've got a whole website dedicated to how search works. Just click right here. Want to read the search quality rater guidelines for yourself? Click right here.