What are the most common reasons a web scraper stops working?

The most common reasons a web scraper stops working are:

1. Website structure changed

   • HTML tags, class names, IDs, or page layout changed.
   • Your selector logic no longer finds the right elements.

2. Anti-bot protections

   • The site adds or tightens protections like CAPTCHA, rate limiting, IP blocking, or browser fingerprinting.
   • Requests start getting blocked or served different content.

3. JavaScript-rendered content changed

   • The site starts loading data dynamically instead of in the initial HTML.
   • A scraper that only reads raw HTML can no longer see the needed data.

4. Authentication/session issues

   • Login expires, cookies become invalid, or tokens refresh differently.
   • Scraper loses access to protected pages or APIs.

5. URL or endpoint changes

   • Page URLs, API routes, query parameters, or pagination patterns change.
   • The scraper keeps requesting old or invalid endpoints.

6. Server-side response changes

   • The site changes response format, such as HTML to JSON, or modifies field names.
   • Parsers fail because they expect a different structure.

7. Network or timeout problems

   • Slow responses, temporary outages, DNS issues, or connection resets.
   • Scraper times out or crashes if retries aren’t handled well.

8. Rate limits or throttling

   • The site limits how many requests you can make in a period.
   • Scraper gets empty responses, errors, or temporary bans.

9. Robots.txt or policy enforcement

   • The site updates crawling rules or blocks automated access more aggressively.
   • Scraper may be disallowed or blocked depending on implementation.

10. Third-party dependencies changed

• If the scraper relies on an external library, browser driver, or proxy provider, updates can break compatibility.

If you want, I can also give you:

• a debugging checklist for a broken scraper, or
• a monitoring strategy to catch failures early.