A web crawler (also called a spider or bot) is a program that systematically browses the internet by following links from page to page. Search engines like Google use crawlers to discover and index web content.
A crawler starts with a list of seed URLs. It fetches each page, extracts all hyperlinks, adds new URLs to its queue, and repeats the process. Crawlers respect rules in robots.txt and use sitemaps to find pages. They track visited URLs to avoid duplicates. Large-scale crawlers run thousands of concurrent requests, often distributed across multiple servers.
Handle it deliberately in production scrapers -- most breakage traces back to skipping this step.
USER-country-de-session-task01Add this string to your scraper's proxy credentials and every request in the job shares one exit IP, which keeps web crawler-related behavior consistent across the run. Change "task01" per worker to isolate parallel scrapes.
Isolate the logic for this step so every scraper in the project shares one tested implementation.
Sites change layouts and behavior over time -- recheck this part of the scraper on a schedule, not just at launch.
This works best over residential or ISP IPs, so the target sees ordinary browsing rather than clustered datacenter traffic.
Capture what actually failed so a broken selector or a new status code surfaces instead of getting masked by automatic retries.
A business directory crawler visits 100,000 publicly listed company profiles to compile a database of company names, addresses, and phone numbers from public web pages.
Web crawlers generate high request volumes that can trigger anti-bot systems. Using proxies distributes crawler traffic across many IPs, keeping request rates per IP within acceptable limits.
A crawler discovers pages by following links across a website or the entire web. A scraper extracts specific data from individual pages. In practice, most data collection projects combine both: a crawler finds the pages, and a scraper extracts the data.
For small crawls (under 1,000 pages), proxies are usually unnecessary. For larger crawls, proxies distribute requests across many IPs to avoid being rate-limited by the target server.
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