Anthony Roberto
November 1, 2024
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2
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124
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Scraping
Javascript rendering is a headless browser with a complete infrastructure of proxies and unblocking mechanisms, ideal for large-scale data collection projects. Designed to mimic authentic human interactions, it is less easily detected. Developers can take advantage of its built-in website unblocking capabilities and vast network of proxies. This browser is also equipped to handle challenges such as CAPTCHA resolution, browser fingerprinting and repeated automatic attempts, simplifying the web scraping process.
Why is browser scraping more complicated?
Retrieving web pages rendered in JavaScript poses a challenge, as the content is not immediately present in the initial HTML response. Instead, it is dynamically generated or modified by JavaScript after the page has been loaded. As a result, conventional HTTP requests are not sufficient, as the desired content must first be generated.
What's more, contemporary web applications often use complex frameworks and asynchronous loading, making it difficult to determine when the page has been fully rendered. To retrieve such pages efficiently, you need tools that can execute JavaScript, render the page as a browser would, and interact with dynamic elements. This requires more advanced methods than simple HTTP requests.
Why use Javascript rendering?
As you can see, it all depends on your objective: the more protected the site, the more Javascript rendering is required.
Why use Javascript rendering? At Piloterr, we offer two scraping modes: standard request mode (headless browser) and JS rendering mode (with a graphical interface). Headless browsers in request mode operate without a graphical interface, and, when combined with a proxy, can effectively scrape data. However, bot detection systems can often identify and block them. In contrast, Javascript rendering mode uses a browser with a graphical user interface, which makes it harder for bot protection to detect. The choice of mode depends on your objective: the more secure a website is, the more likely you’ll need Javascript rendering to scrape it successfully.
How do websites detect web scraping?
- CAPTCHA : Websites often use CAPTCHAs to differentiate between human users and bots. By presenting challenges that are difficult for automated systems to solve, CAPTCHAs prevent straightforward scraping attempts.
- Unusual frequency of visits from a single IP : A high volume of requests from a single IP address in a short period is often a red flag for bot activity, as human users rarely generate requests at such a rapid pace.
- Analysis of request headers : Many bots overlook subtle but important details in HTTP headers (e.g., User-Agent, Accept-Language). Inconsistent or missing headers can reveal non-human behavior.
- Repetitive actions : Bots typically perform repetitive actions with precise timing, which differs from the varied and less predictable actions of human users. Websites monitor for these patterns to detect bot-like behavior.
- JavaScript detection : Sites may use JavaScript to load specific content or interactions. Bots that don't execute JavaScript, or execute it in a predictable, non-human way, may be flagged as scrapers.
- IP and User-Agent blocking : Known proxy IPs and user-agent strings associated with bots are often blacklisted to prevent scraping. Additionally, websites may cross-reference IPs with geolocation to identify unusual access patterns.
- Session tracking : Websites use cookies and sessions to track returning users. If a bot consistently refuses or resets cookies, or creates multiple sessions in a short time, it could be flagged.
When should you use Website Rendering instead of Website Crawler?
If your page contains dynamic content injected via JavaScript, you’ll need to use Website Rendering. If the content is static and you can see the necessary HTML tags without additional loading, the Website Crawler will be sufficient.
For more details, see the documentation:
Why use Website Rendering?
Website Rendering / Javascript Rendering is useful for accessing sites protected by anti-bot solutions such as Cloudflare, Datadome or PerimeterX. These protections often block or restrict access from typical scraping methods, such as simple HTTP requests, by detecting unusual behavior or patterns associated with bots.
Using Website Rendering, you can emulate a real browser, allowing JavaScript to load and interact with the page in a more natural way. This approach allows you to bypass anti-bot measures and access dynamic content that might otherwise be hidden or require user interaction. Website rendering also enables complex, dynamically-generated elements to be handled correctly, such as single-page applications (SPAs) or sites that rely heavily on client-side rendering.
How much does this method cost?
At Piloterr, Javascript rendering costs 2 credits per request, for which everything is taken into account: CAPTCHA resolution, proxies, browsers, volume according to subscription. In concrete terms, on the basis of the Premium subscription, i.e. 18,000 credits, you can execute 9,000 queries per month for $49. For the level of technology, don't hesitate to come and try it out.
