Web scraping, also known as web data extraction, is the process of collecting data from websites automatically. It can be an extremely useful technique for gathering large volumes of public data from the web. However, some websites don't like scrapers accessing their data and may try to detect and block them. So how can you scrape while avoiding detection?
The first thing to know is that almost all scraping leaves traces that a website can detect if they are looking. Here are some signals that can get your scraper flagged:
High request volume - If you send too many requests too fast from the same IP address, it will look suspicious to the target site. Use throttling to add delays between requests.No browser headers - Browsers send identifiable headers like User-Agent with each request. Scrapers typically don't send these which can be a red flag. Mimic browser headers to blend in.Scrapy patterns - If your scraping follows very systematic patterns not typical of a human user, the site may be able to detect this. Build in some randomness to click/scroll patterns.Bot mitigation service detections - Many sites use specialized services to detect scrapers based on signals like above. Rotating IPs and proxies can help avoid getting blacklisted.Here are a few more advanced techniques to consider:
Use a real browser through automation tools like Selenium to render pages and click elements like a human would. Harder to detect but slower.Distribute requests across multiple IPs through proxy rotation services and from different geographic regions.Throttle carefully, avoiding patterns but also not going too slow to mimic human browsing behavior.With some tweaking and testing, it's often possible to gather public web data under the radar. But always respect sites that don't want to be scraped by avoiding excessive load. And don't violate Terms of Service which could have legal consequences in some jurisdictions. With some care though, stealth web scraping can unlock all kinds of useful web data.
