# actix_web::http::header::ACCESS_CONTROL_ALLOW_HEADERS - Rust
API documentation for the Rust `ACCESS_CONTROL_ALLOW_HEADERS` constant in crate `actix_web`.
Keywords: rust, rustlang, rust-lang, ACCESS_CONTROL_ALLOW_HEADERS

# [−] [src] Constant actix_web::http::header::ACCESS_CONTROL_ALLOW_HEADERS

    pub const ACCESS_CONTROL_ALLOW_HEADERS: HeaderName

Preflight response indicating permitted HTTP headers.

The Access-Control-Allow-Headers response header is used in response to a preflight request to indicate which HTTP headers will be available via Access-Control-Expose-Headers when making the actual request.

The simple headers, Accept, Accept-Language, Content-Language, Content-Type (but only with a MIME type of its parsed value (ignoring parameters) of either application/x-www-form-urlencoded, multipart/form-data, or text/plain), are always available and don't need to be listed by this header.

This header is required if the request has an Access-Control-Request-Headers header.

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