Google, Bing, and other search engines are crawling all over the web.
Quick Links
- Search Engines and Crawlers
- Robots and the Politeness Factor
Have you ever searched for something on Google and wondered, "How does it know where to look?" The answer is "web crawlers," which search the web and index it so that you can find things easily online. We'll explain.
Search Engines and Crawlers
When you search using a keyword on a search engine like Google or Bing, the site sifts through trillions of pages to generate a list of results related to that term. How exactly do these search engines have all of these pages on file, know how to look for them, and generate these results within seconds?
The answer is web crawlers, also known as spiders. These are automated programs (often called "robots" or "bots") that "crawl" or browse across the web so that they can be added to search engines. These robots index websites to create a list of pages that eventually appear in your search results.
Crawlers also create and store copies of these pages in the engine's database, which allows you to make searches almost instantly. It's also the reason why search engines often include cached versions of sites in their databases.
Related: How to Access a Web Page When It's Down
Site Maps and Selection
So, how do crawlers pick which websites to crawl? Well, the most common scenario is that website owners want search engines to crawl their sites. They can achieve this by requesting Google, Bing, Yahoo, or another search engine to index their pages. This process varies from engine to engine. Also, search engines frequently select popular, well-linked websites to crawlby tracking the number of times that a URL is linked on other public sites.
Website owners can use certain processes to help search engines index their websites, such as
uploading a site map. This is a file containing all the links and pages that are part of your website. It's normally used to indicate what pages you'd like indexed.
Once search engines have already crawled a website once, they will automatically crawl that site again. The frequency varies based on how popular a website is, among other metrics. Therefore, site owners frequently keep updated site maps to let engines know which new websites to index.
Robots and the Politeness Factor
What if a websitedoesn'twant some or all of its pages to appear on a search engine? For example, you might not want people to search for a members-only page or see your 404 error page. This is where the crawl exclusion list, also known as robots.txt, comes into play. This is a simple text file that dictates to crawlers which web pages to exclude from indexing.
Another reason why robots.txt is important is that web crawlers can have a significant effect on site performance. Because crawlers are essentially downloading all the pages on your website, they consume resources and can cause slowdowns. They arrive at unpredictable times andwithout approval. If you don't need your pages indexed repeatedly, then stopping crawlers might help reduce some of your website load. Fortunately, most crawlersstop crawling certain pages based on the rules of the site owner.
Under the URL and title of every search result in Google, you will find a short description of the page. These descriptions are called snippets. You might notice that the snippet of a page in Google doesn't always line up with the website's actual content. This is because many websites have something called "meta tags," which are custom descriptions that site owners add to their pages.
Site owners often come up with enticing metadata descriptions written to make you want to click on a website. Google also lists other meta-information, such as prices and stock availability. This is especially useful for those running e-commerce websites.
Your Searching
Web searching is an essential part of using the internet. Searching the web is a great way to discover new websites, stores, communities, and interests.Every day, web crawlers visit millions of pages and add them to search engines. While crawlers have some downsides, like taking up site resources, they're invaluable to both site owners and visitors.
Related: How to Delete the Last 15 Minutes of Google Search History
FAQs
The web crawler starts with a list of URLs, known as seed URLs, that it should visit first. These seed URLs are typically provided by the owner of the website or by a search engine. The web crawler retrieves the HTML code of the first seed URL and evaluates it to find any links to other pages on the website.
What is a web crawler and how does it work? ›
A web crawler, or spider, is a type of bot that is typically operated by search engines like Google and Bing. Their purpose is to index the content of websites all across the Internet so that those websites can appear in search engine results.
What is the main work of a crawler? ›
Web crawlers access sites via the internet and gather information about each page, including titles, images, keywords, and links within the page. This data is used by search engines to build an index of web pages, allowing the engine to return faster and more accurate search results for users.
How does crawling work? ›
Crawling: Google downloads text, images, and videos from pages it found on the internet with automated programs called crawlers. Indexing: Google analyzes the text, images, and video files on the page, and stores the information in the Google index, which is a large database.
What is a web crawler for kids? ›
A web crawler is an automated program that automatically browses the web and stores information about the webpages it visits. Every time a web crawler visits a webpage, it makes a copy of the page and adds the URL to the index .
Is it illegal to web crawler? ›
If you're doing web crawling for your own purposes, then it is legal as it falls under the fair use doctrine such as market research and academic research. The complications start if you want to use scraped data for others, especially commercial purposes. Quoted from Wikipedia.org, eBay v.
What does a web crawler see? ›
A Web crawler starts with a list of URLs to visit. Those first URLs are called the seeds. As the crawler visits these URLs, by communicating with web servers that respond to those URLs, it identifies all the hyperlinks in the retrieved web pages and adds them to the list of URLs to visit, called the crawl frontier.
What are crawlers explained? ›
A crawler is a program used by search engines to collect data from the internet. When a crawler visits a website , it picks over the entire website's content (i.e. the text) and stores it in a databank. It also stores all the external and internal links to the website.
Why is crawling so important? ›
Crawling is considered the first form of independent movement. It helps develop and enhance our vestibular/balance system, sensory system, cognition, problem solving skills, and coordination. To help your baby succeed at crawling start with exposing them to tummy time while playing and awake at an early age.
What is the goal for crawling? ›
It's a period of childhood development where your baby puts weight on their hands and knees to build strength and stability for future walking. In addition to helping develop future walking skills, crawling also helps develop your baby's balance, sensory system, cognition, problem solving, and coordination.
Full-body exercise.
Bear crawls are great if you want to target the core and shoulders. But you'll also get a great workout in your chest, back, butt, quads, and hamstrings.
What is the purpose of a crawler? ›
A web crawler, crawler or web spider, is a computer program that's used to search and automatically index website content and other information over the internet. These programs, or bots, are most commonly used to create entries for a search engine index.
Are web crawlers still used? ›
It is not as popular as it used to be, however, you can still search for information on the platform and get relevant results. According to SimilarWeb, WebCrawler has only 240,000 monthly visitors, making it not even in the top 100,000 websites in the world.
How do I use Google web crawler? ›
Adding the URL for the document defined in the Feed Client to crawl patterns by using the Content Sources > Web Crawl > Start and Block URLs page. URLs specified in the feed will only be crawled if they pass through the patterns specified on this page.
What is the difference between web spider and crawler? ›
The idea of spider or crawling is to go across the web by following links in the page, gathering the links, fetching the content and storing the content in your database. There is no as such difference between the two as the terminology suggests spider builds a web(not the www) and crawl is about fetching information.
