It might be easy to assume that when you enter something in a search engine, it searches the internet right then and there. Actually, search engines usually conduct their searches through a massive pre-built index.
First comes crawling. The search engine will employ an automated program known as a crawler to discover pages on the internet. An example of a crawler is Googlebot used by Google. Crawler can discover the URL from either the links on pages that it has visited before or through submitted sitemaps. They revisit the page to discover any changes.
Once it discovers the page, the search engine is able to analyze the content of the page. As defined by Google, this step is called indexing. It analyzes data like texts, images, videos, titles, and other details of the page.
There is no guarantee that a page will get crawled or indexed. Many different reasons could result in this not happening.
Once indexed, the search engine must figure out which results to show for a specific query.
When a person conducts a search, the search engine analyses the query and then scans its index for pages that may be related. Using automatic ranking mechanisms, the search engine decides which pages to show and in which order. In the case of Google, for instance, there are said to be hundreds of criteria used to rank pages, relevance included.
As per Bing, the process is not much different – the search engine crawls the webpages, indexes them, and then ranks them based on relevance and quality. Additionally, Bing claims that machine learning helps pick up the useful results out of a vast amount of available web content.
It means that pages are not ranked based on their age or keyword density.
Instead, search engines try to interpret what a user wants and then find a corresponding result.
As an example, a search for “bicycle repair” may yield local results, while “modern bicycle design” will yield other kinds of results.
But there is one more point worth mentioning: there isn’t an exact copy of the Internet inside search engines.
The web is constantly evolving. New pages are added, old pages get updated, and some of the pages are removed. Thus, search engines constantly crawl and update their indexes. Google states that its crawlers visit the web to find new or updated pages, while Bing defines crawling as an ongoing process aimed at making its index useful and up-to-date.
Search engines have to handle duplicates, spam, content that is inaccessible, and pages that aren’t valuable enough to be shown for certain searches. Google even explicitly states that crawling or indexing a certain page doesn’t mean that it will show up in search results.
Thus, in a simplified way it would look as follows:
Crawling finds information → indexing sorts it → ranking selects the most relevant results.
What is amazing about this process is the scale search engines analyze huge amounts of data and do all these processes really fast.
The search bar appears to be just the user interface of a system created to organize the dynamic web.
