/**
 * Convert an internationalized hostname to its ASCII form with the WHATWG URL
 * implementation available in every supported runtime.
 *
 * This intentionally mirrors `node:url.domainToASCII()`'s empty-string
 * failure contract without adding a Node builtin to browser artifacts. Callers
 * still apply their own DNS-label policy after the conversion.
 */
export declare function domainToASCII(value: string): string;
/**
 * Normalize one textual DNS owner for every resolver backend.
 *
 * The returned identity is lowercase ASCII with an optional terminal root dot
 * removed. One root dot on a non-root owner is accepted, while leading,
 * internal, and additional empty labels are rejected. The public hostname API
 * deliberately rejects the bare DNS root (`.`), but preserves other
 * wire-encodable labels such as `*`, `_dmarc`, and `_443._tcp`.
 *
 * Limits are measured after IDNA conversion and in encoded DNS-wire bytes:
 * each label is 1..63 bytes and the complete length-prefixed QNAME, including
 * its terminal zero byte, is at most 255 bytes.
 */
export declare function normalizeDnsOwner(value: string): string | null;
/**
 * Validate and canonicalize the address accepted by `reverse()` without
 * conflating it with a PTR owner name. Scoped IPv6 literals are rejected: a
 * zone identifier is local interface context, not part of a portable reverse
 * DNS address, and backend support for it is inconsistent.
 */
export declare function normalizeReverseIp(value: string): string | null;