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How to Crawl a Website Without Getting Blocked

James Thompson
James Thompson

Scraping and Proxy Management Expert

03-Sep-2024

Web crawling and web scraping are crucial for public data collection. E-commerce companies utilize web crawlers to gather new data from various websites. This information is then leveraged to improve their business and marketing strategies.

However, many technical professionals may encounter being blocked while conducting web scraping activities. If you are also looking for solutions to this problem, the following content will surely be satisfactory.

Why is it blocked during Crawl a Website

There may be several reasons why a website may prevent you from attempting to crawl or crawl it:

1. Anti-Scraping Measures:

  • Many websites have implemented technical measures to detect and block automated crawlers or scrapers. This is often done to prevent excessive load on their servers, protect their content, or comply with their terms of service.

2. Rate Limiting:

  • Websites may limit the number of requests that can be made from a single IP address or user agent within a certain time frame. Exceeding these limits can result in temporary or permanent blocks.

3. Robots.txt Restrictions:

  • The website's robots.txt file may explicitly disallow crawling of certain pages or the entire website. Respecting the robots.txt file is considered a best practice for ethical web crawling.

4. IP Blocking:

  • The website's security systems may detect your crawling activity and block your IP address, either temporarily or permanently, as a defense against potential abuse or malicious activity.

5. User Agent Blocking:

  • Some websites may specifically block certain user agent strings associated with known crawlers or bots, in an effort to restrict access to their content.

6. Legal or Contractual Restrictions:

  • The website's terms of service or other legal agreements may prohibit crawling or scraping the website without explicit permission or licensing.

You need to make the scraping tool undetectable in order to extract data from web pages, and its main technical types are simulating real browsers and simulating human behavior. For example, an ordinary user would not make 100 requests to a website within a minute. Here are some tips to avoid being blocked during the crawling process for your reference.

5 Tips on How to Crawl a Website Without Getting Blocked

Use Proxies

If your web scraping tool is sending a large number of requests from the same IP address, the website may end up blocking that IP address. In this case, using a proxy server with different IP addresses can be a good solution. A proxy server can act as an intermediary between your scraping script and the target website, hiding your real IP address. You can start by trying free proxy lists, but keep in mind that free proxies are often slow and less reliable. They may also be identified as proxies by the website, or the IP addresses may already be blacklisted. If you're looking to do more serious web scraping work, using a professional, high-quality proxy service may be a better choice.

Using a proxy with rotating IP addresses can make your scraping activity appear to come from different users, reducing the risk of being blocked. Additionally, if a particular IP address gets banned, you can switch to other available IP addresses and continue your work. Furthermore, residential IP proxies are generally harder to detect and block compared to data center IP proxies.

In summary, leveraging proxy services can effectively help you circumvent website restrictions on IP addresses, enabling more stable and continuous web scraping. Choosing the right proxy service provider is crucial. For example, Scrapeless offers high-quality residential IP proxy services with a massive pool of underlying IP resources, ensuring high speed and stability. Their automatic IP switching feature can significantly reduce the risk of IP blocking while you're performing rapid data scraping.

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Set Real Request Headers

As mentioned, your scraping tool activity should aim to mimic the behavior of a normal user browsing the target website as closely as possible. Web browsers typically send a lot of additional information that HTTP clients or libraries may not.

To set real request headers in a web request, you typically need to use a programming language or a tool that allows you to customize HTTP requests. Here are some common methods using different tools and programming languages:

Using cURL (Command Line)

cURL is a command-line tool for transferring data with URL syntax. You can set headers using the -H option.

language Copy
curl -H "Content-Type: 
application/json" -H "Authorization: 
Bearer your_token" 
https://api.example.com/resource

Using Python (Requests Library)

Python's requests library makes it easy to set headers for HTTP requests.

language Copy
import requests

url = "https://api.example.com/resource"
headers = {
    "Content-Type": "application/json",
    "Authorization": "Bearer your_token"
}

response = requests.get(url, headers=headers)
print(response.text)

Using JavaScript (Fetch API)

In JavaScript, you can use the Fetch API to set headers.

language Copy
fetch('https://api.example.com/resource', {
    method: 'GET',
    headers: {
        'Content-Type': 'application/json',
        'Authorization': 'Bearer your_token'
    }
})
.then(response => response.json())
.then(data => console.log(data))
.catch(error => console.error('Error:', error));

Using Postman (GUI Tool)

Postman is a popular GUI tool for making HTTP requests. Here’s how to set headers in Postman:

  1. Open Postman and create a new request
  2. Select the method (GET, POST, etc.)
  3. Enter the request URL
  4. Go to the "Headers" tab
  5. Add the headers you need by entering the key and value.

Using Node.js (Axios Library)

Axios is a promise-based HTTP client for Node.js and the browser.

language Copy
const axios = require('axios');

const url = 'https://api.example.com/resource';
const headers = {
    'Content-Type': 'application/json',
    'Authorization': 'Bearer your_token'
};

axios.get(url, { headers: headers })
    .then(response => {
        console.log(response.data);
    })
    .catch(error => {
        console.error('Error:', error);
    });

Using Java (HttpURLConnection)

Java provides the HttpURLConnection class to handle HTTP requests.

language Copy
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;

public class HttpRequestExample {
    public static void main(String[] args) {
        try {
            URL url = new URL("https://api.example.com/resource");
            HttpURLConnection conn = (HttpURLConnection) url.openConnection();
            conn.setRequestMethod("GET");
            conn.setRequestProperty("Content-Type", "application/json");
            conn.setRequestProperty("Authorization", "Bearer your_token");

            BufferedReader in = new BufferedReader(new InputStreamReader(conn.getInputStream()));
            String inputLine;
            StringBuffer content = new StringBuffer();
            while ((inputLine = in.readLine()) != null) {
                content.append(inputLine);
            }
            in.close();
            conn.disconnect();

            System.out.println(content.toString());
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

These are some of the most common ways to set headers in HTTP requests using different tools and programming languages. Choose the method that best fits your use case and environment.

Use Headless Browsers

To avoid being blocked during the web scraping process, it is best to make your interactions with the target website appear like those of a normal user accessing the URL. An effective way to achieve this is by using headless web browsers. These headless browsers are actual web browsers that can operate without a graphical user interface.

Mainstream browsers like Google Chrome and Mozilla Firefox often support headless mode operation. But even when using the official browsers in headless mode, you need to ensure that their behavior appears sufficiently realistic and natural. Adding certain special request headers, such as the User-Agent header, is a common practice. Selenium and other browser automation suites allow you to combine the use of headless browsers with proxies, which not only hides your IP address but also reduces the risk of being blocked.

Furthermore, we can also use browser fingerprint obfuscation to bypass the detection of headless Chrome.

In summary, by leveraging headless browsers and fingerprint obfuscation techniques, you can create a more natural and difficult-to-detect web crawling environment, effectively reducing the risk of being blocked during the data scraping process.

Use real user agents

Most hosting servers are capable of analyzing the HTTP request headers sent by web crawling bots. This HTTP header, known as the User-Agent, contains a wealth of information ranging from the operating system and software to the application type and its version. Servers can easily detect suspicious User-Agent strings.

Legitimate user agents reflect the common HTTP request configurations submitted by natural human visitors. To avoid being blocked, customizing your user agent to make it appear like a natural, human-like agent is crucial. Given that every request issued by a web browser contains a User-Agent, it is recommended to frequently rotate and switch the User-Agent used by your crawling program. This helps to mimic the behavior of natural users and evade detection.

By carefully managing the user agent and maintaining a natural web crawler profile, you can significantly reduce the risk of being blocked or detected by the target website.

Beware of honeypot traps

Honeypots refer to hidden links embedded in web page HTML code that are invisible to normal users but can be detected by web crawlers. These honeypots are used to identify and block automated bots, as only machines would follow those links.

Due to the relatively significant amount of work required to set up effective honeypots, this technique has not seen widespread adoption across the internet. However, if your requests are being blocked and your crawler activity is detected, the target website may be utilizing honeypot traps to identify and prevent automated scraping.

Conclusion

When collecting public data, the focus should be on avoiding being blacklisted during the crawling process, rather than worrying about preventive measures. The key is to properly configure the browser parameters, be mindful of fingerprint detection, and watch out for honeypot traps. Most importantly, using reliable proxies and respecting the policies of the websites being crawled are crucial to ensuring a smooth public data collection process without encountering any obstacles.

At Scrapeless, we only access publicly available data while strictly complying with applicable laws, regulations, and website privacy policies. The content in this blog is for demonstration purposes only and does not involve any illegal or infringing activities. We make no guarantees and disclaim all liability for the use of information from this blog or third-party links. Before engaging in any scraping activities, consult your legal advisor and review the target website's terms of service or obtain the necessary permissions.

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