Search engines like Google crawl and index websites to gather information about web pages and make it available to users when they perform search queries. The process of crawling and indexing is essential for search engines to provide relevant search results.
They use automated software programs called web crawlers or spiders to discover new web pages. These crawlers start with a list of known web pages (seed URLs) and follow links from one page to another. When they encounter a new URL, they add it to their list for future crawling.
The crawlers send HTTP requests to the web servers hosting the web pages they want to crawl. These requests instruct the webserver to send back the HTML content of the requested page. Once the web page’s HTML is retrieved, the crawler parses it to extract relevant information, such as links to other pages, text content, meta tags, and other elements. The crawler follows the links on the page to discover additional pages to crawl. This process continues recursively, allowing search engines to explore the interconnected web.
After crawling a web page, the search engine’s indexing system processes the content extracted from the page. This includes analyzing text, extracting keywords, and understanding the page’s structure. The search engine stores information about the page in its index, a vast database that contains data about a wide array of web pages. This information includes the page’s URL, content, keywords, and other metadata.
It’s important to note that the crawling and indexing process is ongoing and continuous. Search engines constantly revisit and recrawl websites to ensure that their indexes remain up-to-date and accurate. Additionally, search engines prioritize the most authoritative and relevant pages for indexing and ranking, which is determined by factors such as content quality, backlinks, and user engagement.