A web crawler is a program that browses the web automatically, following links from page to page to discover content. Search engines use crawlers to find and index pages, but businesses use them too.
This guide explains how web crawlers work, how they differ from scrapers, and where proxies fit in.
How a web crawler works
A crawler starts with a list of URLs, visits each one, and follows the links it finds to discover new pages. It repeats this over and over to map large parts of the web.
Search engines like Google use crawlers to keep their index fresh, while companies use them to map sites and find data sources.
Crawler vs scraper
People often mix up crawling and scraping, but they are different jobs.
- A crawler discovers and maps pages by following links
- A scraper extracts specific data from those pages
- Crawling answers what pages exist, scraping answers what is on them
- Many projects crawl first to find pages, then scrape the data
Why crawlers use proxies
Large crawls send many requests, which can trigger blocks or rate limits. Proxies spread the load across many IPs so the crawler can cover more ground without being stopped.
Clean residential or datacenter proxies keep a crawl running smoothly at scale.
Building a responsible crawler
Respect robots rules, crawl at a sensible speed, and avoid hammering servers. A well behaved crawler gets more data and causes fewer problems.
Related reading
Web crawling vs web scraping | What is web scraping | Best web scraping proxies
Final verdict
A web crawler is the discovery engine of the web, mapping pages by following links, while a scraper pulls the data. At scale a crawler needs proxies to avoid blocks, so pair it with a clean pool and crawl responsibly.
What is a web crawler?
A web crawler is a program that browses the web automatically, following links from page to page to discover content. Search engines use crawlers to index the web.
How does a web crawler work?
It starts with a list of URLs, visits each, and follows the links it finds to discover new pages, repeating to map large parts of the web.
What is the difference between a crawler and a scraper?
A crawler discovers and maps pages by following links, while a scraper extracts specific data from those pages. Many projects crawl first, then scrape.
Do web crawlers use proxies?
Yes. Large crawls send many requests, so proxies spread the load across IPs to avoid blocks and rate limits.
How do I build a responsible crawler?
Respect robots rules, crawl at a sensible speed, and avoid overloading servers, which keeps your crawler effective and well behaved.