Web Crawler

1. Overview

Definition: A web crawler, also known as a web spider or web bot, is a program or automated script that browses the World Wide Web in a methodical, automated manner.
Purpose: The primary purpose of web crawlers is to index content for search engines, allowing them to retrieve web pages and make them searchable.
Functionality:
- Starts from a list of URLs (seed URLs).
- Visits each URL and retrieves its content.
- Follows hyperlinks on the page to discover new URLs.
- Updates the index with new information and pages.
Types of Crawlers:
- Search Engine Crawlers: Focused on indexing content for search engines (e.g., Googlebot).
- Data Scraper Crawlers: Tailored for extracting specific data from web pages.
- Site Auditing Crawlers: Used for website analysis and SEO auditing.
Challenges:
- Handling large volumes of data efficiently.
- Complying with robots.txt files that dictate crawling permissions.
- Managing duplicate content and link structures.