--- title: "CORS - Glossary | MDN" chunk: 1/3 source: "https://developer.mozilla.org/en-US/docs/Glossary/CORS" category: "reference" tags: "web, html, css, javascript, documentation" date_saved: "2026-05-05T05:26:05.917812+00:00" instance: "kb-cron" --- * [Skip to main content](https://developer.mozilla.org/en-US/docs/Glossary/CORS#content) * [Skip to search](https://developer.mozilla.org/en-US/docs/Glossary/CORS#search) [ MDN ](https://developer.mozilla.org/en-US/) HTML [HTML: Markup language](https://developer.mozilla.org/en-US/docs/Web/HTML) HTML reference * [Elements](https://developer.mozilla.org/en-US/docs/Web/HTML/Reference/Elements) * [Global attributes](https://developer.mozilla.org/en-US/docs/Web/HTML/Reference/Global_attributes) * [Attributes](https://developer.mozilla.org/en-US/docs/Web/HTML/Reference/Attributes) * [See all…](https://developer.mozilla.org/en-US/docs/Web/HTML/Reference "See all HTML references") HTML guides * [Responsive 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[Glossary](https://developer.mozilla.org/en-US/docs/Glossary) 2. [CORS](https://developer.mozilla.org/en-US/docs/Glossary/CORS) # CORS **CORS** (Cross-Origin Resource Sharing) is a system, consisting of transmitting [HTTP headers](https://developer.mozilla.org/en-US/docs/Glossary/HTTP_header), that determines whether browsers block frontend JavaScript code from accessing responses for cross-origin requests. The [same-origin security policy](https://developer.mozilla.org/en-US/docs/Web/Security/Defenses/Same-origin_policy) forbids cross-origin access to resources. But CORS gives web servers the ability to say they want to opt into allowing cross-origin access to their resources. ## In this article * [CORS headers](https://developer.mozilla.org/en-US/docs/Glossary/CORS#cors_headers) * [See also](https://developer.mozilla.org/en-US/docs/Glossary/CORS#see_also) ## [CORS headers](https://developer.mozilla.org/en-US/docs/Glossary/CORS#cors_headers) [`Access-Control-Allow-Origin`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Access-Control-Allow-Origin) Indicates whether the response can be shared. [`Access-Control-Allow-Credentials`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Access-Control-Allow-Credentials) Indicates whether or not the response to the request can be exposed when the credentials flag is true. [`Access-Control-Allow-Headers`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Access-Control-Allow-Headers) Used in response to a preflight request to indicate which HTTP headers can be used when making the actual request. [`Access-Control-Allow-Methods`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Access-Control-Allow-Methods) Specifies the method or methods allowed when accessing the resource in response to a preflight request. [`Access-Control-Expose-Headers`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Access-Control-Expose-Headers) Indicates which headers can be exposed as part of the response by listing their names. [`Access-Control-Max-Age`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Access-Control-Max-Age) Indicates how long the results of a preflight request can be cached. [`Access-Control-Request-Headers`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Access-Control-Request-Headers) Used when issuing a preflight request to let the server know which HTTP headers will be used when the actual request is made. [`Access-Control-Request-Method`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Access-Control-Request-Method) Used when issuing a preflight request to let the server know which [HTTP method](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Methods) will be used when the actual request is made. [`Origin`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Origin) Indicates where a fetch originates from. [`Timing-Allow-Origin`](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Timing-Allow-Origin) Specifies origins that are allowed to see values of attributes retrieved via features of the [Resource Timing API](https://developer.mozilla.org/en-US/docs/Web/API/Performance_API/Resource_timing), which would otherwise be reported as zero due to cross-origin restrictions. ## [See also](https://developer.mozilla.org/en-US/docs/Glossary/CORS#see_also) * [Cross-Origin Resource Sharing (CORS)](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/CORS) * [Cross-origin resource sharing](https://en.wikipedia.org/wiki/Cross-origin_resource_sharing) on Wikipedia * [Fetch specification](https://fetch.spec.whatwg.org/)