Every time you scrape data, you have one deeper fear of getting blocked!
Is this fear legitimate?
Most websites are out there to serve human visitors and don’t like somebody scraping their site. Many of them block the web crawlers and scrapers because they affect the performance of the site. Not each one will have anti-scraping mechanism in place but as it affects the user experience, they won’t entertain web scraping. Moreover, they don’t have to believe in open data policy which is another reason why they block the web scrapers and crawlers.
That’s why you keep wondering all the time how to extract data without getting blocked.
So you keep working on the puzzle: what’s the best way to scrape the data without getting blocked?
When you try the search engines, there are many things that come up and there are no straightforward and ready answers.
Here’re the key criteria to keep in mind while scraping so that you don’t get blocked:
Delay time between two requests
- When a human visitor accesses a web page, the speed is understandably less compared to what happens in web scraping. When you crawl a site, it takes no time to extract data from different urls and you can do it simultaneously.
- This sort of scraping of data can extract the data in a far quicker way and this speed creates huge traffic on the site and leads to heavy load that can make the website owner suspicious.
- When the site suspects that you are not a human user, it will most naturally assume that you have malicious intentions. So it will also naturally block you.
- This is not an insoluble puzzle. Basically, after a few trial runs, you should be able to find out the ideal crawling speed. Once you do that, put in place some throttling mechanism that can adjust the crawling speed automatically based on the load on the site. Don’t harass the site. Be a little nice to the site that you extract data from so that you can keep scraping it without getting blocked due to your bad behavior!
- You can also put some random programmatic delays in between requests so that it appears like a human user is accessing the site. It also allows you to ensure that you don’t create load for the site. It would be a good idea to decrease concurrent page accessing to 2-3 pages each time.
Use Proxy Servers
- When a site observes that there are a number of requests and data is getting extracting by the same, single ip address, it gets suspicious and eventually blocks the ip. It means you will no longer be able to access the data you want. Too bad, right?
- That’s not the end of the world though; all you need to do is avoid scraping data from a single ip. Instead, use many ips and proxy services and use them randomly so that it makes the site think that the request is getting generated from different servers. So if you use create a pool of ip addresses and randomly use different ip addresses for requests, it becomes increasingly difficult for the site to detect that you are a scraper or crawler.
- In addition, there are different methods available to change your ips. Services such as TOR, VPNs etc. are paid services which provide proxy ips. Some commercial service providers can also help you rotate ip addresses.
Extract data using different logic
- Sites have ways to study the search patterns and detect that it’s not a human visitor who is extracting information from the site. Humans are not consistent in the way they access a site. They will go in a zig-zag fashion. But web scraping follows the consistent and persistent pattern. Anti-scraping mechanisms of a site can easily detect such a pattern.
- Scraping the data is not like the behavior of a human user. In fact, extracting data is more repetitive and persistent so it is easy to detect it. Therefore, you should your logic every now and then.
- Moreover, you should include some random clicks on different pages. Random mouse movements consistent with human user can also give an impression of a human visitor accessing the site.
Use Different Useragent
- Best solution for prevent getting block to rotate different useragent header. Rotate user agent header for each and every request to a common web browser.
Keep eyes on anti-scraping tools
- Since web scraping is rampant in today’s world, sites have begun to equip themselves in terms of how to deal with it.
- Based on the unusual traffic or high download rate, the sites can get suspicious particularly when it is from a single user or single ip. This enables them to distinguish between a human user and a scraper.
- Many sites install anti-scraping tools like ScrapeShield and Bot Defender etc. which can detect web crawling and scraping.
- Therefore, it is necessary to take a moment and study the anti-scraping mechanisms that a site has in place and work out your scraping strategy and tool accordingly.
- It requires some practice before you can use it effectively but it’s worth the effort because it gives longevity to your web scraping efforts. In the long run, it will pay off because you will be able to continue to scrape data without getting blocked!
Last but not the least, you must keep it in mind that when you scrape a site in a way that violates the Terms of Service, you are asking for legal trouble. You could face legal action with respect to the violation of one or several parts of the Terms of Service. You could also be liable for common and even criminal proceedings (See CFAA). So it would be a good idea to respect the Terms of Service every time you indulge in web scraping.
So if your objective is to continue to scrape the data you want and not get blocked, steer clear of the warning signs mentioned throughout the article. Stick to the basic good behavior that sites can tolerate and you will survive longer in the web scraping world than you might think without getting blocked!