What measures does Aliexpress have in place to prevent web scraping?

Aliexpress, like many other large e-commerce platforms, takes various measures to prevent web scraping. These measures are intended to protect their data, intellectual property, and also to ensure the stability and security of their services. Here are some common anti-scraping techniques that sites like Aliexpress may employ:

1. User-Agent Verification: Websites often check the User-Agent string sent by the client (browser or scraping tool) to identify if it comes from a known browser or a bot. Scraping tools that do not rotate or simulate real browsers' User-Agent strings can be easily blocked.

2. CAPTCHAs: If the system detects unusual activity from a user, such as too many requests in a short time, it may present a CAPTCHA challenge to verify that the user is a human and not an automated script.

3. IP Rate Limiting: Aliexpress can limit the number of requests an IP address can make in a certain timeframe. Exceeding this limit might lead to temporary or permanent IP bans.

4. Dynamic Content: Websites can serve content dynamically using JavaScript, making it more difficult for scrapers that cannot execute JavaScript to access the data.

5. Request Headers Checking: Websites can check for certain headers that browsers typically send with requests (like Accept-Language, Referer, etc.). If these headers are missing or appear to be tampered with, the request may be blocked.

6. Token Validation: Anti-CSRF tokens or session-based tokens may be used to ensure that requests to the server are legitimate and generated from the site's own pages.

7. Fingerprinting: More sophisticated fingerprinting techniques can analyze a combination of attributes (like IP address, user agent, behavior patterns, etc.) to identify and block web scrapers.

8. Obfuscated HTML/CSS: Changing classes, IDs, and other selectors regularly or using non-human-readable values can make it harder for scrapers to locate the data they are trying to extract.

9. API Restrictions: Aliexpress may have an API, and typically APIs have more stringent rate limits and require authentication which can limit unauthorized scraping.

10. Legal Measures: They have terms of service that prohibit unauthorized scraping, and they can take legal action against offenders.

11. Server-Side Detection Algorithms: They can use server-side algorithms to detect non-human browsing patterns such as high-speed navigation, repetitive actions, etc.

12. Content Delivery Networks (CDNs): CDNs can provide an additional layer of security, such as detecting and blocking scrapers before they even reach the main servers.

13. Honeypots: Hidden links or traps in the website's code can detect scrapers that follow all links indiscriminately.

As a developer or a company, it is crucial to be aware of these measures and to respect the terms of service of the website you wish to scrape. If you need data from Aliexpress, the recommended approach is to use their official API if available, or to seek permission for scraping if necessary. Unauthorized web scraping could result in legal consequences and permanent bans from the site.

Remember, this answer is provided for educational purposes and does not condone or encourage violating Aliexpress's or any other service's terms of use.