What Is a Web Crawler and How Does It Work?

Indexing is quite an essential process as it helps users find relevant queries within seconds. The search indexing can be compared to the book indexing. For instance, if you open the last pages of a textbook, you will find an index with a list of queries in alphabetical order and pages where they are mentioned in the textbook. The same principle underlines the search index, but instead of page numbering, a search engine shows you some links where you can look for answers to your inquiry.

The significant difference between the search and book indices is that the former is dynamic, therefore, it can be changed, and the latter is always static.
How Does a Web Search Work?

Before plunging into the details of how a crawler robot works, let’s see how the whole search process is executed before you get an answer to your search query.

For instance, if you type “What is the distance between Earth and Moon” and hit enter, a search engine will show you a list of relevant pages. Usually, it takes three major steps to provide users with the required information to their searches:

A web spider crawls content on websites
It builds an index for a search engine
Search algorithms rank the most relevant pages

Also, one needs to bear in mind two essential points:

You do not do your searches in real-time as it is impossible

There are plenty of websites on the World Wide Web, and many more are being created even now when you are reading this article. That is why it could take eons for a search engine to come up with a list of pages that would be relevant to your query. To speed up the process of searching, a search engine crawls the pages before showing them to the world.

You do not do your searches in the World Wide Web

Indeed, you do not perform searches in the World Wide Web but in a search index and this is when a web crawler enters the battlefield.