/** Tracks and persists the document referrer in both session and local storage. */
export declare class Referrer {
    private static storageId;
    local: string;
    session: string;
    constructor();
    /**
     * Returns the referrer data as a JSON object, or undefined if both values are empty.
     * @returns An object with local and session referrer strings, or undefined
     */
    toJson(): {
        local: string;
        session: string;
    } | undefined;
    private getFromLocal;
    private getFromSession;
}
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