Googlebot
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| Original author(s) | |
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| Type | Web crawler |
| Website | Googlebot FAQ |
Googlebot is the search bot software used by Google, which collects documents from the web to build a searchable index for the Google Search engine.
If a webmaster wishes to restrict the information on their site available to a Googlebot, or another well-behaved spider, they can do so with the appropriate directives in a robots.txt file, or by adding the meta tag <meta name="Googlebot" content="nofollow" /> to the web page. Googlebot requests to Web servers are identifiable by a user-agent string containing "Googlebot" and a host address containing "googlebot.com".
Currently, Googlebot follows HREF links and SRC links. There is increasing evidence Googlebot can execute JavaScript and parse content generated by Ajax calls as well. There are many theories regarding how advanced Googlebot's ability is to process JavaScript, with opinions ranging from minimal ability derived from custom interpreters. Googlebot discovers pages by harvesting all the links on every page it finds. It then follows these links to other web pages. New web pages must be linked to from other known pages on the web in order to be crawled and indexed or manually submitted by the webmaster.
A problem which webmasters have often noted with the Googlebot is that it takes up an enormous amount of bandwidth. This can cause websites to exceed their bandwidth limit and be taken down temporarily. This is especially troublesome for mirror sites which host many gigabytes of data. Google provides "Webmaster Tools" that allow website owners to throttle the crawl rate.
How often Googlebot will crawl a site depends on the crawl budget. Crawl budget is an estimation of how often a website is updated. A site's crawl budget is determined by how many incoming links it has and how frequent the site is updated.
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