Security & Web Utilities • Published August 18, 2026

CORS Headers Reference: Allow-Methods, Allow-Headers, Expose-Headers & Max-Age

Complete reference for all CORS HTTP headers: Access-Control-Allow-Origin, Methods, Headers, Expose-Headers, Max-Age, and Request headers.

Comprehensive developer reference guide to all 8 standard CORS HTTP headers: syntax, permitted values, browser support, and practical examples.

Frequently Asked Questions

Q1. Why can my frontend JavaScript not read response headers like X-Total-Count?

By default, browsers only expose "CORS-safelisted" response headers (Cache-Control, Content-Language, Content-Type, Expires, Last-Modified, Pragma) to JavaScript. To expose custom headers, the server must include Access-Control-Expose-Headers: X-Total-Count.