One of the main challenges of scraping the web is avoiding getting blocked by the websites you are scraping. Websites may block bots for various reasons, such as to protect themselves against unwanted actions or to prevent bandwidth overload.
Getting blocked can result in losing access to valuable data sources, and wasting time and resources. Therefore, it is useful to follow some best practices to help you evade blocking while extracting the data you need from the web.
In this article, we will discuss some measures you should adopt to avoid getting blocked when scraping websites.
Respect the website's robots.txt
One of the first and most important steps to avoid getting blocked when scraping websites is to respect their robots.txt file. Every website has a document known as robots.txt that offers guidelines on how bots (like web scrapers and search engines) should interact with the site. This document tells bots which parts of the website are open for scraping and which are not.
A robots.txt file is a text file that is read by search engines and other web crawlers to let them know which pages they are allowed to crawl on a website.
Before you start scraping, check out this file - it's usually located at www.[website].com/robots.txt. Respecting the robots.txt file helps you stay within the permitted areas of the website and face little to no difficulties when scraping it programmatically.
Avoid Cloudflare errors
Cloudflare is a service that provides security and performance optimization for websites. It acts as a reverse proxy that filters out malicious or unwanted traffic from reaching the website's server.
Cloudflare errors are some of the most common challenges that web scrapers face. Here are some best guides from ZenRows to avoid such errors as Cloudflare Error 1020.
Bypassing Obstacles: Use CAPTCHA Solving Services
Some websites use CAPTCHA (Completely Automated Public Turing test to tell Computers and Humans Apart) to block bots. If you've ever had to identify fire hydrants or traffic lights in a grid of images, you've encountered a CAPTCHA.
CAPTCHA solving services can help you bypass these. They use a combination of Optical Character Recognition (OCR) technology and real human workers to solve CAPTCHAs, allowing your web scraping to continue unhindered.
A CAPTCHA is a challenge-response test websites use to verify whether a request originates from a human or a bot. A CAPTCHA may require you to solve a puzzle, type some text, or perform some other task that is easy for humans but hard for bots.
Utilize proxies and IP rotation
A proxy is an intermediary server that acts as a gateway between your web scraper and the target website. Proxies can hide your original IP address and location, making it appear like you are accessing the website from a different source.
Using proxies and IP rotation, a technique that allows you to change your IP address periodically using a pool of different proxies can help you avoid getting blocked by reducing the chances of getting detected as a bot by the website and reduces the chances of getting blocked by geo-restrictions or firewalls.
Emulate human behavior
Emulating human behavior is the key to avoiding getting blocked in web scraping. Some websites may monitor their user behavior, such as uniform patterns, mouse movements, or request timing. By emulating regular human behavior with your web scraper, you can blend in with the normal user traffic and avoid drawing attention.
You can emulate human behavior by:
- Simulating mouse movements and varying request timing: Some websites may track your mouse movements and clicks to determine if you are a human or a bot. You should use tools that simulate mouse movements and clicks on the website, such as Selenium or Puppeteer. Likewise, it is a good practice to vary your request timing by adding random delays or pauses between requests to make them more natural and unpredictable.
- Using real User-Agent headers: A User Agent is a string that identifies your browser and device to the website. Using the User Agent of a real browser in your web scraper request header will make your request similar to that of a regular user.
- Setting your fingerprint right: Fingerprinting is a technique websites use to identify and track users based on their browser and device characteristics, such as screen size, fonts, plugins, or cookies. You should set your fingerprint right by randomizing these characteristics in your web scraper configuration.
The Gentle Approach: Rate Limiting
Flood a website with too many requests too quickly and it's like knocking on someone's door incessantly - you're likely to get a less-than-friendly response. In the context of web scraping, that response is getting your IP address blocked.
To avoid this, be gentle. Use rate limiting to control the number of requests you send in a given timeframe. For instance, you might start by sending one request every ten seconds, and then gradually increase the rate if you're not encountering issues. This way, you won't overwhelm the website's server.
Conclusion
Web scraping is a potent tool for gathering data from the web, but it needs to be done responsibly and intelligently to avoid getting blocked. By understanding and implementing the strategies we've outlined here, you can maintain a healthy and productive relationship with the websites you scrape, collecting the data you need without causing unnecessary disruption. Remember, the key is to be respectful and considerate of the websites you scrape.