Web Error Codes

FixerCode maintains an independent, curated reference of 96 web error codes across 5 technologies. The web category covers HTTP status codes (the protocol-level response language defined by RFC 9110), web server errors from Nginx and similar servers, edge-level errors from content delivery networks like Cloudflare, Chromium network errors (ERR_*) generated by the browser's network stack before an HTTP response is received, and CORS cross-origin policy errors enforced by the browser's Same-Origin Policy.

Web error codes span four layers: protocol-level HTTP status codes that any web server or API can return, server-specific codes that Nginx and other servers define for edge cases outside the HTTP standard, CDN-specific codes (such as Cloudflare's 520–526 range) that indicate failures between the edge and the origin server, and client-side errors (Chromium ERR_ codes and CORS policy blocks) that occur in the browser before or during an HTTP request. Understanding which layer produced the code is the first step in diagnosis.

Each code page includes a plain-language explanation of what the code means, a list of common causes, frequently asked questions, and links to related codes within the same response family or across other categories. All entries are independently researched and are not affiliated with any vendor mentioned on this site.