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Increased HTTP header size limit to 128 KB

Cloudflare Fundamentals

CDN now supports 128 KB request and response headers 🚀

We're excited to announce a significant increase in the maximum header size supported by Cloudflare's Content Delivery Network (CDN). Cloudflare now supports up to 128 KB for both request and response headers.

Previously, customers were limited to a total of 32 KB for request or response headers, with a maximum of 16 KB per individual header. Larger headers could cause requests to fail with HTTP 413 (Request Header Fields Too Large) errors.

What's new?

  • Support for large headers: You can now utilize much larger headers, whether as a single large header up to 128 KB or split over multiple headers.
  • Reduces 413 and 520 HTTP errors: This change drastically reduces the likelihood of customers encountering HTTP 413 errors from large request headers or HTTP 520 errors caused by oversized response headers, improving the overall reliability of your web applications.
  • Enhanced functionality: This is especially beneficial for applications that rely on:
    • A large number of cookies.
    • Large Content-Security-Policy (CSP) response headers.
    • Advanced use cases with Cloudflare Workers that generate large response headers.

This enhancement improves compatibility with Cloudflare's CDN, enabling more use cases that previously failed due to header size limits.

To learn more and get started, refer to the Cloudflare Fundamentals documentation.