Many websites use various anti-bot mechanisms to detect and prevent bots like web scrapers from accessing their content. The most prominent techniques include IP blocking, CAPTCHA tests, honeypot traps, and device or browser fingerprinting.
Top 5 Patterns Websites Detect as Bot Activity
Most websites will block your web scraper if you do the following.
Sending multiple simultaneous HTTP requests from one IP address
Sending several simultaneous HTTP requests from one IP address may not block your web scraper, but raising that number to tens or hundreds will. It appears as a bot-like activity because a human can’t send that many concurrent HTTP requests.
Not adding random delays between requests
Sending multiple HTTP requests without randomised delays doesn’t appear human. If you were to extract data manually, you would make random pauses at intervals. A bot doesn’t need a break.
Sending HTTP requests at the same time of day
Scraping a particular website at the same time of day leaves a digital fingerprint. Browser fingerprinting mechanisms flag that activity as bot-like because it indicates a programmed web scraper.
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Always following an identical web scraping pattern
People don’t follow an identical pattern when browsing websites. Bots like web scrapers do because it’s in their programming.
Not simulating human-like behaviour
All the instances above showcase bot-like behaviour, but other factors can also make your web scraper appear as such.
For instance, your target websites might look for the User-Agent string in the HTTP request header to identify your web browser, OS, and other configurations. However, most web scrapers don’t set that string, failing to imitate authentic users.
Is It Possible To Overcome Anti-Bot Systems?
Overcoming anti-bot measures may seem complicated, but you only need to do the following:
- Adjust HTTP request times – Adding random delays between concurrent HTTP requests will make your web scraper appear human-like. Intervals of 10–20 seconds should do the trick.
- Use rotating HTTP headers – Rotating your HTTP headers will trick the target website servers into believing your requests are coming from multiple organic users. The User-Agent header is crucial to alter, but don’t forget about the Accept, Accept-Encoding, and others.
- Set a Referrer – The Referrer header lets target website servers know where users are coming from, so set it before every session to make your web scraper seem organic. For instance, it can be “https://www.google.com/,” “https://www.google.co.uk/,” a social media platform, or a random site.
- Leverage headless browsers – Anti-bot systems look at headers, cookies, extensions, JavaScript rendering, fonts, and other browser parameters to determine if organic users are sending HTTP requests. Since that isn’t the case with web scrapers, a headless browser can make them undetectable because it won’t render images, graphics, and other CSS stylesheet and JavaScript elements.
- Use a web scraper API – These solutions are excellent for bypassing CAPTCHA tests. They can also deploy headless browsers and ensure JavaScript rendering and real-time HTML tracking, perfect for scraping dynamic websites. You can also use CAPTCHA-solving solutions, although they can be costly and slow.
- Respect the robots.txt file – Many websites have a robots.txt file to specify which pages web crawlers and scrapers can access. However, some add a hidden link to that file to set honeypot traps. Only bots can see it, so obey the rules to avoid it.
Proxy servers are another solution to web scraping blocks, but they deserve a separate spot.
Proxy Servers
Proxies are secure gateways between web browsers and target website servers. They send HTTP requests from their IP addresses, routing the traffic and concealing users’ IP addresses.
Many proxy types exist, but the best for overcoming blocks when scraping the web include the following:
- Residential proxies – The best way to avoid blocks is to use a residential proxy server because it lets you choose a home-based IP address, making it the least detectable. You can pick a country or city to access localised content, bypass geo-restrictions, and enjoy human-like scraping (without honeypot traps). Find one that frequently rotates IP addresses to avoid CAPTCHA tests, IP blocks, and other anti-bot techniques.
- Shared datacenter proxy servers – Use these solutions if you don’t mind sharing an IP address (computer-generated) with multiple simultaneous users. They come from data centers and are more affordable than residential proxies. However, they’ may be slower and are easier to detect.
- Dedicated datacenter proxy servers – High anonymity, privacy, performance, and speed characterise these solutions because they support one simultaneous user. Their price tag is higher, but like their shared counterparts, they’re also detectable since they come from data centers.
A residential proxy is your best bet for human-like web scraping.
Anti-bot mechanisms can make web scraping frustrating. However, you can bypass them with residential proxies, rotating HTTP headers, headless browsers, web scraper APIs, and other tools and methods.
We’ve only scratched the surface, so explore other solutions for extracting relevant data without encountering blocks.