diff --git a/src/client/state/export.ts b/src/client/state/export.ts
new file mode 100644
index 0000000..55e6058
--- /dev/null
+++ b/src/client/state/export.ts
@@ -0,0 +1,121 @@
+import type { CustomEvents, CustomGames } from "../../shared/custom.ts";
+import type { DailyLogMap } from "./useDailyLog.ts";
+import type { Prefs } from "./usePrefs.ts";
+import type { ProgressMap } from "./useProgress.ts";
+
+export interface ExportData {
+  format: "gacha-tracker-export";
+  version: 1;
+  exportedAt: string;
+  progress: Record<string, unknown>;
+  daily: DailyLogMap;
+  ignored: Record<string, { at: string }>;
+  customGames: CustomGames;
+  customEvents: CustomEvents;
+  prefs?: Prefs | undefined;
+}
+
+export interface ParsedImport {
+  progress: ProgressMap | null;
+  daily: DailyLogMap | null;
+  ignored: Record<string, { at: string }> | null;
+  customGames: unknown;
+  customEvents: unknown;
+  prefs: unknown | null;
+}
+
+/**
+ * Builds the serializable JSON export object.
+ * When `prefs` is provided, includes preferences for moving hosts ("Export all").
+ * When omitted, exports progress and custom data only ("Export").
+ */
+export function buildExportData(
+  progress: Record<string, unknown>,
+  daily: DailyLogMap,
+  ignored: Record<string, { at: string }>,
+  own: { games: CustomGames; events: CustomEvents },
+  prefs?: Prefs | undefined,
+): ExportData {
+  return {
+    format: "gacha-tracker-export",
+    version: 1,
+    exportedAt: new Date().toISOString(),
+    progress,
+    daily,
+    ignored,
+    customGames: own.games,
+    customEvents: own.events,
+    ...(prefs !== undefined ? { prefs } : {}),
+  };
+}
+
+/**
+ * Validates and parses raw JSON from an import file.
+ * Returns null if the file is not a valid Event Clock export.
+ */
+export function parseImportData(parsed: unknown): ParsedImport | null {
+  if (typeof parsed !== "object" || parsed === null) return null;
+  const data = parsed as {
+    format?: string;
+    progress?: unknown;
+    completions?: unknown;
+    daily?: unknown;
+    ignored?: unknown;
+    customGames?: unknown;
+    customEvents?: unknown;
+    prefs?: unknown;
+  };
+  if (data.format !== "gacha-tracker-export") return null;
+
+  const asRecord = (v: unknown) =>
+    typeof v === "object" && v !== null
+      ? (v as Record<string, unknown>)
+      : null;
+  const asMarks = (v: unknown) =>
+    typeof v === "object" && v !== null
+      ? (v as Record<string, { at: string }>)
+      : null;
+
+  let progress: ProgressMap | null = asRecord(data.progress) as ProgressMap | null;
+  const legacy = asRecord(data.completions) as Record<string, { at: string }> | null;
+  if (progress === null && legacy !== null) {
+    progress = Object.fromEntries(
+      Object.entries(legacy).map(([id, m]) => [id, { ...m, status: "done" }]),
+    );
+  }
+
+  const daily =
+    typeof data.daily === "object" && data.daily !== null
+      ? (data.daily as DailyLogMap)
+      : null;
+  const ignored = asMarks(data.ignored);
+  const prefs =
+    typeof data.prefs === "object" && data.prefs !== null ? data.prefs : null;
+
+  return {
+    progress,
+    daily,
+    ignored,
+    customGames: data.customGames,
+    customEvents: data.customEvents,
+    prefs,
+  };
+}
+
+/**
+ * Initiates a browser download of a JSON object as a file.
+ */
+export function triggerDownload(data: unknown, filename: string): void {
+  const blob = new Blob([JSON.stringify(data, null, 2)], {
+    type: "application/json",
+  });
+  const url = URL.createObjectURL(blob);
+  const a = document.createElement("a");
+  a.href = url;
+  a.download = filename;
+  a.style.display = "none";
+  document.body.append(a);
+  a.click();
+  a.remove();
+  setTimeout(() => URL.revokeObjectURL(url), 0);
+}
diff --git a/src/client/state/usePrefs.ts b/src/client/state/usePrefs.ts
index 6a1aa5b..5eec284 100644
--- a/src/client/state/usePrefs.ts
+++ b/src/client/state/usePrefs.ts
@@ -6,7 +6,7 @@ import type { SortMode } from "./sort.ts";
 import { KEYS, readJson, writeJson } from "./storage.ts";
 import type { TimelineGroup } from "./lanes.ts";
 import { DEFAULT_THEME_CHOICE, type ThemeChoice } from "./theme.ts";
-import { DEFAULT_DAY_WIDTH } from "./zoom.ts";
+import { DEFAULT_DAY_WIDTH, snapDayWidth } from "./zoom.ts";
 
 /**
  * Which of the two views the reader is looking at.
@@ -62,11 +62,11 @@ export interface Prefs {
    * `JSON.stringify` drops it on the way to storage.
    *
    * Not a key space and not a migration: one more field in the single `prefs`
-   * blob, like `timelineGroup`. It rides the export for free, though note that
-   * `importProgress` restores progress, dailies, ignores and the reader's own
-   * games — never prefs — so an imported file does not bring an order back.
-   * That asymmetry predates this field and applies to region, theme and view
-   * alike.
+   * blob, like `timelineGroup`. It rides the export for free. Standard
+   * progress import restores progress, dailies, ignores and the reader's own
+   * games — leaving local prefs intact — while "Import all" restores preferences
+   * alongside them, bringing game order, region, theme and active games back
+   * when migrating hosts.
    */
   gameOrder?: LaneId[] | undefined;
   /**
@@ -269,6 +269,95 @@ export function adoptRenamed(
   return { ...rest, showUpcoming: timelineUpcoming };
 }
 
+/**
+ * Takes incoming preferences (e.g. from an imported backup file) and restores a
+ * clean, type-safe Prefs object, falling back to defaults for any missing or
+ * invalid values.
+ */
+export function restorePrefsValue(incoming: unknown): Prefs {
+  const base = defaults();
+  if (typeof incoming !== "object" || incoming === null) {
+    return base;
+  }
+  const raw = adoptRenamed(incoming as Partial<Prefs> & { timelineUpcoming?: boolean });
+  const result: Prefs = {
+    ...base,
+    ...raw,
+  };
+
+  // Region
+  if (result.region !== "america" && result.region !== "europe" && result.region !== "asia") {
+    result.region = base.region;
+  }
+
+  // Games arrays
+  if (!Array.isArray(result.hiddenGames)) {
+    result.hiddenGames = base.hiddenGames;
+  } else {
+    result.hiddenGames = result.hiddenGames.filter((g): g is LaneId => typeof g === "string");
+  }
+
+  if (result.knownGames !== undefined) {
+    if (!Array.isArray(result.knownGames)) {
+      delete result.knownGames;
+    } else {
+      result.knownGames = result.knownGames.filter((g): g is LaneId => typeof g === "string");
+    }
+  }
+
+  if (result.gameOrder !== undefined) {
+    if (!Array.isArray(result.gameOrder)) {
+      result.gameOrder = undefined;
+    } else {
+      result.gameOrder = result.gameOrder.filter((g): g is LaneId => typeof g === "string");
+    }
+  }
+
+  // focusGame
+  if (result.focusGame !== null && typeof result.focusGame !== "string") {
+    result.focusGame = null;
+  }
+
+  // Sort
+  if (result.sort !== "ending" && result.sort !== "doing") {
+    result.sort = base.sort;
+  }
+
+  // View
+  if (result.view !== "soon" && result.view !== "timeline") {
+    result.view = base.view;
+  }
+
+  // Zoom
+  if (typeof result.timelineDayWidth === "number") {
+    result.timelineDayWidth = snapDayWidth(result.timelineDayWidth);
+  } else {
+    result.timelineDayWidth = base.timelineDayWidth;
+  }
+
+  // Timeline grouping
+  if (result.timelineGroup !== "game" && result.timelineGroup !== "ending") {
+    result.timelineGroup = base.timelineGroup;
+  }
+
+  // Theme
+  if (result.theme !== "dark" && result.theme !== "light" && result.theme !== "system") {
+    result.theme = base.theme;
+  }
+
+  // Booleans
+  result.showUpcoming = typeof result.showUpcoming === "boolean" ? result.showUpcoming : base.showUpcoming;
+  result.timelineSplitUpcoming = typeof result.timelineSplitUpcoming === "boolean" ? result.timelineSplitUpcoming : base.timelineSplitUpcoming;
+  result.detectDaily = typeof result.detectDaily === "boolean" ? result.detectDaily : base.detectDaily;
+  result.showChores = typeof result.showChores === "boolean" ? result.showChores : base.showChores;
+  result.showCompleted = typeof result.showCompleted === "boolean" ? result.showCompleted : base.showCompleted;
+  result.showIgnored = typeof result.showIgnored === "boolean" ? result.showIgnored : base.showIgnored;
+  result.regionConfirmed = typeof result.regionConfirmed === "boolean" ? result.regionConfirmed : base.regionConfirmed;
+  result.onboarded = typeof result.onboarded === "boolean" ? result.onboarded : base.onboarded;
+
+  return result;
+}
+
 export function usePrefs() {
   const [prefs, setPrefs] = useState<Prefs>(() => ({
     ...defaults(),
@@ -283,6 +372,10 @@ export function usePrefs() {
     setPrefs((prev) => ({ ...prev, ...patch }));
   }, []);
 
+  const restorePrefs = useCallback((incoming: unknown) => {
+    setPrefs(restorePrefsValue(incoming));
+  }, []);
+
   const toggleGame = useCallback((game: LaneId) => {
     setPrefs((prev) => ({
       ...prev,
@@ -292,5 +385,6 @@ export function usePrefs() {
     }));
   }, []);
 
-  return { prefs, update, toggleGame };
+  return { prefs, update, toggleGame, restorePrefs };
 }
+
diff --git a/test/prefs.test.ts b/test/prefs.test.ts
index 31c1305..ddfc035 100644
--- a/test/prefs.test.ts
+++ b/test/prefs.test.ts
@@ -1,5 +1,5 @@
 import { describe, expect, test } from "bun:test";
-import { adoptNewLanes, adoptRenamed, defaults } from "../src/client/state/usePrefs.ts";
+import { adoptNewLanes, adoptRenamed, defaults, restorePrefsValue } from "../src/client/state/usePrefs.ts";
 import type { LaneId } from "../src/shared/custom.ts";
 
 /**
@@ -123,3 +123,77 @@ describe("defaults that a reader would notice losing", () => {
     expect({ ...defaults(), ...stored }.showChores).toBe(true);
   });
 });
+
+describe("restorePrefsValue", () => {
+  test("returns defaults when passed null or non-object", () => {
+    expect(restorePrefsValue(null)).toEqual(defaults());
+    expect(restorePrefsValue(undefined)).toEqual(defaults());
+    expect(restorePrefsValue("invalid")).toEqual(defaults());
+  });
+
+  test("restores full valid preferences from an export", () => {
+    const exported = {
+      region: "asia" as const,
+      hiddenGames: ["genshin", "hsr"],
+      knownGames: ["genshin", "hsr", "zzz"],
+      gameOrder: ["zzz", "genshin"],
+      focusGame: "zzz",
+      sort: "doing" as const,
+      view: "timeline" as const,
+      timelineDayWidth: 48,
+      timelineGroup: "ending" as const,
+      showUpcoming: true,
+      timelineSplitUpcoming: false,
+      detectDaily: true,
+      showChores: false,
+      showCompleted: false,
+      showIgnored: true,
+      theme: "light" as const,
+      regionConfirmed: true,
+      onboarded: true,
+    };
+    expect(restorePrefsValue(exported)).toEqual(exported);
+  });
+
+  test("falls back to defaults for missing fields from older exports", () => {
+    const older = {
+      region: "europe" as const,
+      hiddenGames: ["zzz"],
+      theme: "dark" as const,
+    };
+    const restored = restorePrefsValue(older);
+    expect(restored.region).toBe("europe");
+    expect(restored.hiddenGames).toEqual(["zzz"]);
+    expect(restored.theme).toBe("dark");
+    // missing fields use defaults
+    expect(restored.showChores).toBe(defaults().showChores);
+    expect(restored.timelineGroup).toBe(defaults().timelineGroup);
+    expect(restored.sort).toBe(defaults().sort);
+  });
+
+  test("adopts renamed fields like timelineUpcoming to showUpcoming", () => {
+    const legacy = {
+      timelineUpcoming: true,
+    };
+    const restored = restorePrefsValue(legacy);
+    expect(restored.showUpcoming).toBe(true);
+  });
+
+  test("sanitizes corrupt or invalid fields", () => {
+    const corrupt = {
+      region: "mars",
+      hiddenGames: "not-an-array",
+      gameOrder: 123,
+      timelineDayWidth: -99,
+      theme: "neon",
+      view: "grid",
+    };
+    const restored = restorePrefsValue(corrupt);
+    expect(restored.region).toBe(defaults().region);
+    expect(restored.hiddenGames).toEqual([]);
+    expect(restored.gameOrder).toBeUndefined();
+    expect(restored.timelineDayWidth).toBe(defaults().timelineDayWidth);
+    expect(restored.theme).toBe(defaults().theme);
+    expect(restored.view).toBe(defaults().view);
+  });
+});
diff --git a/test/progress.test.ts b/test/progress.test.ts
index 103930d..19f371b 100644
--- a/test/progress.test.ts
+++ b/test/progress.test.ts
@@ -1,4 +1,6 @@
 import { describe, expect, test } from "bun:test";
+import { buildExportData, parseImportData } from "../src/client/state/export.ts";
+import { restorePrefsValue } from "../src/client/state/usePrefs.ts";
 import { mergeProgress } from "../src/client/state/useProgress.ts";
 import type { ProgressMap } from "../src/client/state/useProgress.ts";
 
@@ -70,3 +72,106 @@ describe("mergeProgress", () => {
     expect(Object.keys(mergeProgress(device, {})).sort()).toEqual(["a", "b"]);
   });
 });
+
+describe("buildExportData", () => {
+  const dummyOwn = { games: {}, events: {} };
+
+  test("progress export omits prefs", () => {
+    const data = buildExportData({ a: { status: "done" } }, {}, {}, dummyOwn);
+    expect(data.format).toBe("gacha-tracker-export");
+    expect(data.version).toBe(1);
+    expect(data.prefs).toBeUndefined();
+    expect(data.progress).toEqual({ a: { status: "done" } });
+  });
+
+  test("export all includes prefs", () => {
+    const prefs = { region: "asia" } as any;
+    const data = buildExportData({ a: { status: "done" } }, {}, {}, dummyOwn, prefs);
+    expect(data.format).toBe("gacha-tracker-export");
+    expect(data.version).toBe(1);
+    expect(data.prefs).toEqual(prefs);
+  });
+});
+
+describe("parseImportData", () => {
+  test("returns null for non-objects or invalid format", () => {
+    expect(parseImportData(null)).toBeNull();
+    expect(parseImportData("string")).toBeNull();
+    expect(parseImportData({ format: "unknown" })).toBeNull();
+  });
+
+  test("parses export with progress, daily, ignored, and prefs", () => {
+    const file = {
+      format: "gacha-tracker-export",
+      version: 1,
+      progress: { "event:1": { status: "done" as const, at: "2026-08-10T12:00:00.000Z" } },
+      daily: { "dailies:genshin": { days: ["2026-08-10"], at: "2026-08-10T12:00:00.000Z" } },
+      ignored: { "event:2": { at: "2026-08-10T12:00:00.000Z" } },
+      customGames: { "mygame:test": { id: "mygame:test" } },
+      customEvents: { "myevent:test": { id: "myevent:test" } },
+      prefs: { region: "europe", hiddenGames: ["zzz"] },
+    };
+    const parsed = parseImportData(file);
+    expect(parsed).not.toBeNull();
+    expect(parsed?.progress).toEqual(file.progress);
+    expect(parsed?.daily).toEqual(file.daily as any);
+    expect(parsed?.ignored).toEqual(file.ignored);
+    expect(parsed?.customGames).toEqual(file.customGames);
+    expect(parsed?.customEvents).toEqual(file.customEvents);
+    expect(parsed?.prefs).toEqual(file.prefs);
+  });
+
+  test("maps legacy completions to progress with status done", () => {
+    const file = {
+      format: "gacha-tracker-export",
+      version: 1,
+      completions: { "legacy:1": { at: "2026-08-10T12:00:00.000Z" } },
+    };
+    const parsed = parseImportData(file);
+    expect(parsed?.progress).toEqual({
+      "legacy:1": { at: "2026-08-10T12:00:00.000Z", status: "done" as const },
+    });
+    expect(parsed?.prefs).toBeNull();
+  });
+
+  test("full migration round-trip preserves active games, order, and region", () => {
+    const originalPrefs = {
+      region: "asia" as const,
+      hiddenGames: ["genshin"],
+      gameOrder: ["zzz", "hsr", "genshin"],
+      theme: "light" as const,
+      sort: "doing" as const,
+    };
+    const progress = {
+      "event:1": { status: "doing" as const, at: "2026-08-10T12:00:00.000Z" },
+    };
+    const own = {
+      games: { "mygame:custom": { id: "mygame:custom", name: "Custom", hue: "#ff0000", at: "..." } },
+      events: {},
+    };
+
+    // 1. Export all creates payload with prefs
+    const exportedAll = buildExportData(progress, {}, {}, own, originalPrefs as any);
+    const jsonString = JSON.stringify(exportedAll);
+
+    // 2. Import parses the file
+    const imported = parseImportData(JSON.parse(jsonString));
+    expect(imported).not.toBeNull();
+    expect(imported?.prefs).not.toBeNull();
+
+    // 3. restorePrefsValue restores the exact preferences
+    const restored = restorePrefsValue(imported!.prefs);
+    expect(restored.region).toBe("asia");
+    expect(restored.hiddenGames).toEqual(["genshin"]);
+    expect(restored.gameOrder).toEqual(["zzz", "hsr", "genshin"]);
+    expect(restored.theme).toBe("light");
+    expect(restored.sort).toBe("doing");
+
+    // 4. In contrast, standard progress export has null prefs on import
+    const exportedProgressOnly = buildExportData(progress, {}, {}, own);
+    const importedProgressOnly = parseImportData(JSON.parse(JSON.stringify(exportedProgressOnly)));
+    expect(importedProgressOnly?.prefs).toBeNull();
+  });
+});
+
+