A simple but powerful web crawler library in C#

• Obeys robots.txt (crawl delay & allow/disallow)
• Obeys in-page robots rules (X-Robots-Tag header and <meta name="robots" /> tag)
• Uses sitemap.xml to seed the initial crawl of the site
• Built around a parallel task async/await system
• Swappable request and content processors, allowing greater customisation
• Auto-throttling (see below)

The crawler is built around fast but "polite" crawling of website. This is accomplished through a number of settings that allow adjustments of delays and throttles.

You can control:

• Number of simulatenous requests
• The delay between requests starting (Note: If a crawl-delay is defined for the User-agent, that will be the minimum)
• Artificial "jitter" in request delays (requests seem less "robotic")
• Timeout for a request before throttling will apply for new requests
• Throttling request backoff: The amount of time added to the delay to throttle requests (this is cumulative)
• Minimum number of requests under the throttle timeout before the throttle is gradually removed

• Control the UserAgent used in the crawling process
• Set additional host aliases you want the crawling process to follow (for example, subdomains)
• The max number of retries for a specific URI
• The max number of redirects to follow
• The max number of pages to crawl

using InfinityCrawler;

var crawler = new Crawler();
var result = await crawler.Crawl(new Uri("http://example.org/"), new CrawlSettings {
	UserAgent = "MyVeryOwnWebCrawler/1.0",
	RequestProcessorOptions = new RequestProcessorOptions
	{
		MaxNumberOfSimultaneousRequests = 5
	}
});