import { StorageItemMap } from 'webext-storage';
type TabId = number;
type Origin = string;
export type ActiveTab = {
    id: TabId;
    origin: Origin;
};
/**
 * The list is not guaranteed to be up to date. The activeTab permission might be lost before it's detected.
 */
export declare const possiblyActiveTabs: StorageItemMap<string, string | undefined> | Map<string, string>;
declare function startActiveTabTracking(): void;
declare function stopActiveTabTracking(): void;
export declare const PRIVATE: {
    startActiveTabTracking: typeof startActiveTabTracking;
    stopActiveTabTracking: typeof stopActiveTabTracking;
};
export declare const onActiveTab: {
    addListener(callback: (tab: ActiveTab) => void): void;
    removeListener: (callback: import("simple-event-target").SimpleEventListener<ActiveTab>) => void;
};
export declare const onActiveTabLost: {
    addListener(callback: (tabId: TabId) => void): void;
    removeListener: (callback: import("simple-event-target").SimpleEventListener<number>) => void;
};
export {};