Cloudflare Anti Scraping may Break Your React SSR

If you're using React server-side rendering (SSR) with Cloudflare, you might encounter an unexpected issue where your server-rendered content doesn't match the client-side render. Here's how I discovered and solved this puzzling problem.

The Mystery

Recently, I noticed that my React SSR application was throwing hydration errors in production. Everything worked perfectly in development, but something was clearly off once deployed behind Cloudflare.

Investigation

After comparing the server-rendered HTML with the client-side rendered version using a diff checker, I discovered something interesting: Cloudflare's Scrape Shield feature was automatically obfuscating certain elements:

• Email addresses were being encoded by Scrape Shield
• Font references were being modified by Cloudflare Fonts
• JavaScript content was being transformed by RocketLoader

This explained why React was complaining about hydration mismatches - the server and client renders were literally different!

The Solution

The fix turned out to be simple but not immediately obvious. Cloudflare's Scrape Shield, Cloudflare Fonts, and Cloudflare RocketLoader while well-intentioned, was interfering with my SSR setup.

Lessons Learned

This experience highlights an important consideration when using SSR with CDN services: security features designed to protect against scraping can interfere with legitimate rendering processes. Always test your SSR implementation thoroughly when adding such services to your stack.

When debugging SSR issues:

1. Compare server and client HTML output
2. Check for any middleware or CDN features that might modify your HTML
3. Test with and without protection features enabled

Remember that while security features are important, they need to be balanced with your application's functional requirements.