TL;DR: Every time you search, there are thousands (sometimes millions!) of webpages or other types of content that might be a match. Google uses its robust systems to present the most helpful information in response to your search. Let’s take a closer look at how Google Search works, from the results you see to the spam you don’t.
To learn even more about Search visit How Search Works
How Google Search organizes information
Finding information by crawling
Most of our Search index is built through the work of software known as crawlers. These automatically visit publicly accessible webpages and follow links on those pages, much like you would if you were browsing content on the web. Crawlers go from page to page to organize the content of the web in Google’s Search index.
Organizing information by indexing
When crawlers find a webpage, our systems render the content of the page, just as a browser does. We take note of key signals — from keywords to website freshness — and we keep track of it all in the Search index.
The Google Search index contains hundreds of billions of webpages and is well over 100,000,000 gigabytes in size. It’s like the index in the back of a book — with an entry for every word seen on every webpage we index. When we index a webpage, we add it to the entries for all of the words it contains.
How results are automatically generated
With the vast amount of information available, finding what you need would be nearly impossible without some help sorting through it. Google Search systems are designed to filter through hundreds of billions of webpages at lighting speed.
Key factors that help determine which results are returned for your query:
Meaning: To return relevant results, we first need to establish what you’re looking for ー the intent behind your query. To do this, we build language models to try to decipher how the relatively few words you enter into the search box match up to the most useful content available.
Relevance: Next, our systems analyze the content to assess whether it contains information that might be relevant to what you are looking for.
Quality: After identifying relevant content, our systems aim to prioritize those that seem most helpful. To do this, they identify signals that can help determine which content demonstrates expertise, authoritativeness, and trustworthiness.
Useability: Our systems also consider the usability of content. When all things are relatively equal, content that people will find more accessible may perform better.
Context: Information such as your location, past Search history, and Search settings all help us to ensure your results are what is most useful and relevant for you in that moment.
Improving Search with rigorous testing
Our goal is always to provide you with the most useful and relevant information. Any changes we make to Search are always to improve the usefulness of results you see. That’s why we never accept payment from anyone to be included in Search results.
Testing for usefulness
Search has changed over the years to meet the evolving needs and expectations of the people who use Google. From innovations like the Knowledge Graph, to updates to our systems that ensure we’re continuing to surface relevant content, our goal is always to improve the usefulness of your results.
We put all possible changes to Search through a rigorous evaluation process to analyze metrics and decide whether to implement a proposed change.
Data from these evaluations and experiments go through a thorough review by experienced engineers and search analysts, as well as other legal and privacy experts, who then determine if the change is approved to launch.
Detecting spam to bring you relevant and reliable results
Google invests in systems to ensure that sites don’t rise in Search results through deceptive or manipulative behavior. This is especially important because spam sites can harm or mislead people.
Why we fight against spam
Spam sites attempt to game their way to the top of Search results through a variety of techniques such as repeating keywords over and over, or showing Google content that’s different from what users see (something that’s known as “cloaking”). Hackers sometimes even get into legitimate sites and change them into spam sites that might redirect people into scams or worse.
How we target spam
Our automated systems can detect the vast majority of spam and keep it out of your top Search results, similar to how a good email system keeps spam from flooding your inbox.
The rest of spam is tackled manually by our spam removal team, who review pages and flag them if they violate the Webmaster Guidelines. When we take manual action on content, we try to alert the creator to help them address issues.
How Search keeps you safe
Whether it’s browsing incognito, encrypting your search, or providing tools for family safety—Google works to make every search secure.
Guided by our privacy principles, we create tools and explanations to help you understand how we use data to make Search more helpful to you.
For example, using your search history, Google can autocomplete your searches. So if you start to search for “barcelona”, autocomplete might predict past places or sights you searched for before you’ve even finished typing them.
If you want to dive deeper into any of these tools, you can learn more about all of these systems at our How Search Works hub.