import type { Fetch } from "./builtin-types.js";
import type { Headers } from "./types.js";
export declare const createResponseHeaders: (headers: Awaited<ReturnType<Fetch>>['headers']) => Record<string, string>;
/**
 * Copies headers from "newHeaders" onto "targetHeaders",
 * using lower-case for all properties,
 * ignoring any keys with undefined values,
 * and deleting any keys with null values.
 */
export declare function applyHeadersMut(targetHeaders: Headers, newHeaders: Headers): void;
export interface HeadersProtocol {
    get: (header: string) => string | null | undefined;
}
export type HeadersLike = Record<string, string | string[] | undefined> | HeadersProtocol;
export type HeadersInit = [string, string][] | Record<string, string> | Headers;
export declare const isHeadersProtocol: (headers: any) => headers is HeadersProtocol;
export declare const getRequiredHeader: (headers: HeadersLike | Headers, header: string) => string;
export declare const getHeader: (headers: HeadersLike | Headers, header: string) => string | undefined;
//# sourceMappingURL=headers.d.ts.map