A web crawler, also known as a spider, is a program that automatically browses the web to collect data and create an index for search engines. It starts with a list of known URLs (seed URLs), visits these pages, extracts new links, and adds them to its queue for later crawling. This process is repeated recursively, allowing the crawler to discover and index vast amounts of web content.
- Starting Point:- Crawlers begin with a list of seed URLs, which can be a starting point for a website or a collection of known URLs.
- Visiting Pages:- The crawler connects to the web servers associated with the URLs and downloads the content of the webpage.
- Extracting Links:- The crawler analyses the downloaded page and identifies hyperlinks (links to other pages).
- Adding to Queue:- These newly discovered URLs are added to a crawl queue, which is a list of pages to be visited later.
- Following Links:- The crawler then selects URLs from the crawl queue, following the defined policies (like prioritisation based on backlinks, page views, etc.).
- Indexing:- As the crawler visits pages, it extracts relevant information (text, metadata, etc.) and stores it in a massive index, which is essentially a database of web content.
- Prioritisation:- Crawlers prioritise certain pages based on factors like backlinks, page views, and domain authority, ensuring the most valuable and relevant content is indexed.
- Regular Updates:- Crawlers revisit websites periodically to check for updates and changes to the content, ensuring the index remains up-to-date.
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