What is a Web Crawler & How Does it Work?

How does a web crawler work?

Web crawlers start from a list of known URLs and crawl these webpages first. After this, web crawlers find hyperlinks to other URLs, and the next step is to crawl them. As a result, this process can be endless. This is why web crawlers will follow particular rules. For example, what pages to crawl, when they should crawl these pages again to check for content updates, and much more.

Furthermore, web crawler bots can be used by companies that need to gather data for their purposes. In this case, a web crawler is usually accompanied by a web scraper that downloads, or scrapes, required information. Note, web scraping and web crawling are not the same, as scraping aims to parse and extract data from a website while the web crawling process is more focused on discovering target URLs. We have a dedicated crawler vs scraper blogspot discussing the topic in great detail, so if you're curious to learn more, check it out.

Another crucial aspect to look out for is web crawler speeds. If your requirements are high, and you wish to crawl, let’s say a hundred thousand pages, very few web crawlers will be able to achieve your data gathering needs, especially in a quick manner. Furthermore, crawling multiple threads at high speeds may break the server of the page you’re crawling, thus impacting the owners of said server and your own projects. Therefore, ensuring your web crawling tools are used in an ethical manner is beneficial for everyone and should be a top priority. Sometimes to mitigate crawling through entire threads of a website, a robot.txt file gets introduced to direct crawlers as to which pages ought to be crawled and how frequently.

Types of crawlers

When discussing the various types of crawlers, there are usually three categories to list.

1. Desktop crawler. These crawlers mimic user behavior and are commonly run through computers or browsers installed on desktops. As a result, these crawlers can effectively make HTTP requests and gather the results easily.

2. API-Based Crawlers. The core feature of these web crawler bots is that they don’t crawl the pages themselves. The requests are instead sent to API endpoints, from whom the specific structured data is gathered.

3. Cloud-Based Crawlers. A key feature of these crawlers is that their crawling workload is distributed across multiple machines or instances, allowing for increased scalability and performance. This makes could-based crawlers perfect for large-scale crawling tasks.

What is an example of a web crawler?

In general, web crawlers are created for the work of search engines. Search engines use web crawlers to index websites and deliver the right pages according to keywords and phrases. Every search engine uses its own web crawlers. Google, for example, uses Googlebot, which encompasses two types of web crawlers: Googlebot Desktop and Googlebot Smartphone. Notably, Google primarily indexes the mobile version of the content, so the vast majority of Googlebot crawl requests are made using the mobile crawler.

Various providers offer web crawlers, like Screaming Frog, for companies that prefer to make data-driven decisions. For example, in e-commerce, there are specific web crawlers that are used to crawl information that includes product names, item prices, descriptions, reviews, and much more. Furthermore, web crawlers are used to discover the most relevant and gainful keywords from search engines and track their performance.

What is Oxylabs Web Crawler?

The Web Crawler tool is a feature of Oxylabs Web Scraper API for crawling any website, selecting useful content, and having it delivered to you in bulk. With the help of this feature, you can discover all pages on a website and get data from them at scale and in real time. To check how our Web Crawler works in action, watch the video below.

Most common web crawling use cases for business

Data collection

Large e-commerce websites use web scraping tools to gather data from competitors’ websites. For example, companies crawl and scrape websites and search engines to gather real-time competitors’ price data. This allows businesses to monitor competitors’ campaigns and promotions, and act accordingly.

Monitoring

Another use case includes keeping up to date with the assortment on competitors’ websites. Monitoring new items that other companies add to their product lists allows e-commerce businesses to make decisions about their own product range.

Both of these use cases help companies keep track of their competitors’ actions. Having this information, companies offer new products or services. Being on top of their game is essential if businesses want to stay relevant in the competitive market.

Challenges of web crawling

We already discussed web crawling advantages for your e-commerce business, but this process also raises challenges. 

First of all, data crawling requires a lot of resources. In order to gather wanted data from e-commerce websites or search engines, companies need to develop a certain infrastructure, write scraper code and allocate human resources (developers, system administrators, etc.) 

Another issue is anti-bot measures. Most large e-commerce websites do not want to be scraped and use various security features. For example, websites add CAPTCHA challenges or even block IP addresses. Many budget scraping and crawling tools on the market are not efficient enough to gather data from large websites. 

Some companies use proxies and rotate them in order to mimic real customer’s behavior. Rotating IPs works on small websites with basic logic, but more sophisticated e-commerce websites have extra security measures in place. They quickly identify bots and block them.

One more challenge: the quality of the gathered data. If you extract information from hundreds or thousands of websites every day, it becomes impossible to manually check the quality of data. Cluttered or incomplete information will inevitably creep into your data feeds. 

Oxylabs’ E-Commerce Scraper API – the ultimate web crawling solution

Oxylabs’ E-Commerce Scraper API (part of Web Scraper API) solves e-commerce data gathering challenges by offering a simple solution. E-Commerce Scraper API is a powerful tool that gathers real-time information and sends the data back to you. It functions both as a web crawler and a web scraper.

Most importantly, this tool is perfect for scraping large and complicated e-commerce websites and search engines, so you can forget blocked IPs and broken data.