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Table of Contents

What is a crawler?
How does a web crawler work?
Different types of crawlers
Controlling crawlers
Crawlers and SEO

What is a crawler?

A crawler, also known as a web crawler, is a software program that is increasingly used by search engines to automatically search theWorld Wide Weband build anindex.

When searching websites, the crawler analyzes and indexes their content so that it can be read more quickly by search engines later on. It lays the foundation, so to speak, for the work of search engines.

How does a web crawler work?

A crawler is programmed for repetitive actions and therefore worksautomatically.

The information found during "crawling" is assigned to specific categories and then indexed, making it available for retrieval and evaluation. Texts, images, videos, and links are all included in the analysis.

Different types of crawlers

There are many different crawlers, some examples being Googlebot and Bingbot. Even Alexa has its own bot called ia_archiever.

Crawlers can also perform various tasks, such asdata mining. This involves searching the web for specific information. For example, email addresses can be searched for. This is sometimes used byblack hat SEOsto send spam emails to the collected email addresses.

Another area of responsibility would be plagiarism detection. This function is particularly important when it comes to legal violations relating to copyrighted material.

Control crawlers

Mit Hilfe von Meta-Tags können dem Crawler im <head> Bereich Anweisungen gegeben werden, so kann man unter anderem steuern, ob der Crawler eine Seite indiziert oder einem Link folgt.

Example of an instruction that the address should not be indexed and no links should be followed:

<meta name=“robots“ content=“noindex,nofollow“>

 Instructions can also be sent to crawlers using therobots.txt file.

Crawlers and SEO

Part ofsearch engine optimizationinvolves designing a website in such a way that it can be optimally read by the crawler, ensuring that all content is included in the search engine index. A logicalURL structure is helpful in this regard. In addition,backlinksand clear internal links encourage the crawler to visit your website more often and for longer periods of time.