Mingguang SEO Training: Web crawler crawling strategies that you must know when outsourcing website optimization

With the explosion of Internet information, people are no longer satisfied with relying solely on traditional methods such as open directories to find things on the Internet. In order to meet the different needs of different people, web crawlers emerged. A web crawler refers to a program component or script that automatically captures information on the Internet according to certain rules. In search engines, a web crawler is an automated program that the search engine uses to discover and crawl documents. Web crawlers are one of the basic knowledge that Baidu SEO optimization company personnel should learn. Knowing and understanding web crawlers will help to better optimize the website.

Mingguang SEO Training: Web crawler crawling strategies that you must know when outsourcing website optimization

We know that the two goals of search engine architecture are effectiveness and efficiency, which are also the requirements for web crawlers. Faced with hundreds of millions of web pages, duplicate content is very high. In the SEO industry, the duplication rate may be above 50%. The problem faced by web crawlers is that in order to improve efficiency and effectiveness, they need to obtain more high-quality pages within a certain period of time and discard those pages with low originality, copied content, spliced ​​content, etc.

Generally speaking, there are three types of web crawler strategies: a. Breadth first: Search all links on the current page before entering the next layer; b. Best first: Based on certain web page analysis algorithms, such as link algorithms and page weighting algorithms, more valuable pages are crawled first; c. Depth first: Crawling along a link until there are no more links to a page, and then starting to crawl another one. However, crawling usually starts from seed websites. If this method is adopted, the quality of the crawled pages may become lower and lower, so this strategy is rarely used. There are many types of web crawlers. The following is a brief introduction of the common ones:

1) General web crawler

General web crawlers, also known as "full-net crawlers", start crawling from some seed websites and gradually expand to the entire Internet.

Common web crawler strategies: depth-first strategy and breadth-first strategy.

2) Focus on web crawlers

Focused web crawlers, also known as "topic web crawlers", pre-select one (or a few) relevant topics and crawl and grab only relevant pages in this category.

Focused web crawler strategy: The focused web crawler has added link and content evaluation modules, so the key to its crawling strategy is to evaluate the links and content of the page before crawling.

3) Incremental web crawler

Incremental web crawling refers to updating already indexed pages, crawling new pages, and pages that have changed.

Incremental web crawler strategies: breadth-first strategy and PageRank-first strategy, etc.

4) Deep Web Crawler

The pages that can be crawled and captured by search engine spiders are called "surface web pages", and some pages that cannot be obtained through static links are called "deep web pages". Deep Web crawlers are crawler systems that crawl deep web pages.