What is a web crawler

When it comes to technical SEO, it can be difficult to understand how it works. But it is important to gain as much knowledge as possible to optimize our website and reach a larger audience. One tool that plays an important role in SEO is the web crawler.

A web crawler (also known as a web spider) is a robot that searches and indexes content on the Internet. Essentially, web crawlers are responsible for understanding the content on a web page in order to retrieve it when a query is made.

You may be wondering, "Who runs these web crawlers?"

Typically, web crawlers are operated by search engines that have their own algorithms. The algorithm will tell web crawlers how to find relevant information in response to search queries.

A web spider will search (crawl) and categorize all web pages on the Internet that it can find and is told to index. So, if you don't want your page to be found on search engines, you can tell web crawlers not to crawl your page.

To do this, you need to upload a robots.txt file. Essentially, the robots.txt file will tell search engines how to crawl and index the pages on your website.

For example, let’s look at Nike.com/robots.txt

Nike uses its robots.txt file to determine which links within its website will be crawled and indexed.

In this section of the file, it determines:

The web crawler Baiduspider is allowed to crawl the first 7 links

Web crawler Baiduspider is banned from crawling the remaining three links

This is beneficial to Nike because some of the company's pages are not suitable for search, and the disallowed links will not affect its optimized pages, which Pages help them rank in search engines.

So now we know what web crawlers are and how do they get their job done? Next, let’s review how web crawlers work.

Web crawlers work by discovering URLs and viewing and classifying web pages. In the process, they find hyperlinks to other web pages and add them to the list of pages to crawl next. Web crawlers are smart and can determine the importance of each web page.

Search engine web crawlers will most likely not crawl the entire Internet. Instead, it will determine the importance of each web page based on factors including how many other pages link to it, page views, and even brand authority. Therefore, web crawlers will determine which pages to crawl, the order in which to crawl them, and how often they should crawl updates.

For example, if you have a new web page, or changes are made to an existing web page, the web crawler will record and update the index. Or, if you have a new web page, you can ask search engines to crawl your site.

When a web crawler is on your page, it looks at the copy and meta tags, stores that information, and indexes it for search engines to rank for keywords.

Before the entire process begins, web crawlers will look at your robots.txt file to see which pages to crawl, which is why it is so important for technical SEO.

Ultimately, when a web crawler crawls your page, it determines whether your page will appear on the search results page for your query. It's important to note that some web crawlers may behave differently than others. For example, some people may use different factors when deciding which pages are most important to crawl.

Now that we understand how web crawlers work, we’ll discuss why they should crawl your website.

The above is the detailed content of What is a web crawler. For more information, please follow other related articles on the PHP Chinese website!