It is common for websites to limit/block web crawlers from crawling the web pages. This is because some malicious crawlers often disregard the instructions in the robots.txt file, thereby necessitating taming. While good crawlers first read the file beforehand to determine which pages are a no-go-zone, malicious spiders do not. Yet, crawling can be resource-intensive. Because blocks are standard, it is crucial for proxies to be used alongside crawlers. But before thoroughly going into why you need proxies for web crawling, let’s first discuss what is a web crawler and what is a proxy server.
What is a web crawler?
A web crawler (also known as a spider) is a bot that automatically follows links included in web pages to discover new content as well as new pages. Ideally, the crawler sends HTTP requests and renders HTML pages that servers send as responses. Upon rendering, the crawler parses the code file for URLs leading to other pages (links). It also stores the rendered content in indexes for future retrieval. It is noteworthy that this is how search engines discover new pages. Check out this article from Oxylabs to find out more about the topic.
What is a proxy?
A proxy (also known as a proxy server) is an intermediary between your computer and the web server that anonymizes all requests from your website. It achieves this by assigning a new IP address selected from a vast pool of IPs from different locations. Thanks to this arrangement, you can bypass geo-restrictions, meaning you can access content that is limited to specific jurisdictions.
Why do websites block crawlers?
A website’s loading speed is a key determinant to its ranking on search engine results pages (SERPs). As a result, server-side rendering (SSR), the practice where a server sends a fully rendered page to a web client (browser), is often preferred.
While SSR influences loading speed and promotes the user experience for all users, including those with slow internet connections, it is detrimental in some ways. SSR is resource-intensive and costly. And given that SSR needs to happen whenever a spider is crawling every web page in a website, you can imagine the number of required resources.
And even in cases where websites do not use SSR, they still have to respond to every HTTP request from the crawler. The resources needed are directly proportional to the number of web pages and spiders that will crawl the pages.
This is one of the reasons robots.txt files are used. They contain instructions on the pages that can be crawled. However, and as detailed, some crawlers do not obey the guidelines. This leaves website owners with no choice other than to block web crawling to tame rogue bots that may have malicious intent.
Web owners do this by either blacklisting IP addresses or blocking the crawlers using the User-Agent. The former approach requires fewer server resources and is therefore preferred. For this reason, it is important for you to use a proxy alongside a web crawler to ensure your crawling experience is unimpacted by blacklisting.
Proxies for web crawling
Proxies, which assign a different IP address, thereby anonymizing your browsing experience, are useful in preventing or bypassing IP blacklisting. Ideally, a website owner must collect all the IP addresses associated with crawling activities and include them in the server’s or firewall’s blacklist. Notably, crawling using your computer’s IP address makes it easy for the server to detect unusual traffic and subsequently block your identifier.
However, simply using a proxy server, which anonymizes your crawling, adds a layer of privacy and secrecy. At the same time, if the proxy only assigns you a single IP address, then it will also be blocked. For this reason, it is important to use rotating proxies. This proxy changes the assigned IP address periodically.
It is noteworthy that crawling requires speed. As such, datacenter proxies, which, though virtual, are based in datacenters, are powerful, fast, and way cheaper. The only downside is that they can be easily detected and subsequently blacklisted. To prevent detection, you can use rotating datacenter proxies or residential proxies.
Residential proxies assign IP addresses that belong to actual internet service providers (ISPs) and are, therefore, given to real users. They offer reliability and speed but are expectedly pricey. As is the case with datacenter proxies, however, it is advisable to use rotating residential proxies. This way, the IP address will keep changing, thereby limiting to a minimum the number of requests originating from a single identifier.
Usually, website owners integrate protective measures into their websites and web servers. These measures, which include IP blocking and the use of robots.txt files, aim to protect against rogue bots that harbor malicious intent. Fortunately, in cases where the intention behind using a crawler is not negative, you can bypass these blocks using proxies. Proxy servers will assign your computer a unique IP address, anonymizing the crawler’s activity. Nonetheless, it is crucial to use the right proxy.