diff --git a/client.ts b/client.ts
index d0d02f8..196d2de 100644
--- a/client.ts
+++ b/client.ts
@@ -4,7 +4,7 @@ import { load_gallery_page } from "./page/GalleryPage.ts";
 import { load_home_overview_page } from "./page/HomeOverviewPage.ts";
 import { load_mpv_page } from "./page/MPVPage.ts";
 import { load_single_page } from "./page/SinglePage.ts";
-import { RecoverableError, TimeoutError } from "./utils.ts";
+import { RecoverableError, TimeoutError, toJSON } from "./utils.ts";
 
 export type GID = [number, string];
 
@@ -172,7 +172,7 @@ export class Client {
         if (gids.length > 25) throw Error("Load limiting is reached.");
         const data = { method: "gdata", gidlist: gids, namespace: 1 };
         const re = await this.post(`https://${this.host}/api.php`, {
-            body: JSON.stringify(data),
+            body: toJSON(data),
             headers: { "content-type": "application/json" },
         });
         if (re.status != 200) {
diff --git a/config.ts b/config.ts
index 47a16cf..73880b6 100644
--- a/config.ts
+++ b/config.ts
@@ -1,6 +1,6 @@
 import { exists } from "@std/fs/exists";
 import { JsonValue, parse } from "@std/jsonc";
-import { isDocker } from "./utils.ts";
+import { isDocker, toJSON } from "./utils.ts";
 
 export type ConfigType = {
     cookies: boolean;
@@ -252,5 +252,5 @@ export async function load_settings(path: string) {
 }
 
 export function save_settings(path: string, cfg: Config, signal?: AbortSignal) {
-    return Deno.writeTextFile(path, JSON.stringify(cfg._data), { signal });
+    return Deno.writeTextFile(path, toJSON(cfg._data), { signal });
 }
diff --git a/db.ts b/db.ts
index decb8f4..127c92b 100644
--- a/db.ts
+++ b/db.ts
@@ -9,7 +9,13 @@ import { join, resolve } from "@std/path";
 import { SqliteError } from "sqlite/mod.ts";
 import { SqliteError as Sqlite3Error } from "sqlite3";
 import { Status } from "sqlite/src/constants.ts";
-import { parse_bool, sleep, sure_dir_sync, try_remove_sync } from "./utils.ts";
+import {
+    parse_bool,
+    sleep,
+    sure_dir_sync,
+    toJSON,
+    try_remove_sync,
+} from "./utils.ts";
 import { Task, TaskType } from "./task.ts";
 import { generate as randomstring } from "randomstring";
 import type { GalleryMetadataSingle } from "./page/GalleryMetadata.ts";
@@ -575,7 +581,7 @@ export class EhDb {
     add_ehmeta(data: GalleryMetadataSingle) {
         this.db.query(
             "INSERT OR REPLACE INTO ehmeta VALUES (?, ?, ?);",
-            [data.gid, JSON.stringify(data), new Date()],
+            [data.gid, toJSON(data), new Date()],
         );
     }
     add_gmeta(gmeta: GMeta) {
diff --git a/page/MPVPage.ts b/page/MPVPage.ts
index 633f994..ee73316 100644
--- a/page/MPVPage.ts
+++ b/page/MPVPage.ts
@@ -1,7 +1,7 @@
 import { DOMParser } from "deno_dom/wasm-noinit";
 import { extname } from "@std/path";
 import { Client } from "../client.ts";
-import { initDOMParser } from "../utils.ts";
+import { initDOMParser, toJSON } from "../utils.ts";
 import type { EhFile, PMeta } from "../db.ts";
 
 export type MPVRawImage = {
@@ -255,7 +255,7 @@ class MPVPage {
         };
         if (nl) param.nl = nl;
         const re = await this.client.post(this.api_url, {
-            body: JSON.stringify(param),
+            body: toJSON(param),
             headers: { "content-type": "application/json" },
         });
         if (re.status != 200) {
diff --git a/routes/api/config.ts b/routes/api/config.ts
index 24848b5..143008b 100644
--- a/routes/api/config.ts
+++ b/routes/api/config.ts
@@ -9,6 +9,7 @@ import { parse_bool } from "../../server/parse_form.ts";
 import { return_json } from "../../server/utils.ts";
 import { ExitTarget } from "../../signal_handler.ts";
 import type { User } from "../../db.ts";
+import { toJSON } from "../../utils.ts";
 
 const UNSAFE_TYPE: (keyof ConfigType)[] = [
     "base",
@@ -39,7 +40,7 @@ export const handler: Handlers = {
                 };
                 const sendMessage = (mes: ConfigSeverSocketData) => {
                     if (socket.readyState === socket.OPEN) {
-                        socket.send(JSON.stringify(mes));
+                        socket.send(toJSON(mes));
                     }
                 };
                 const close_handle = () => {
diff --git a/routes/api/task.ts b/routes/api/task.ts
index 95b5b7c..b9d4493 100644
--- a/routes/api/task.ts
+++ b/routes/api/task.ts
@@ -11,6 +11,7 @@ import { return_data, return_error } from "../../server/utils.ts";
 import type { DownloadConfig } from "../../tasks/download.ts";
 import type { ExportZipConfig } from "../../tasks/export_zip.ts";
 import { User, UserPermission } from "../../db.ts";
+import { toJSON } from "../../utils.ts";
 
 export const handler: Handlers = {
     GET(req, ctx) {
@@ -24,7 +25,7 @@ export const handler: Handlers = {
             e: CustomEvent<Task | TaskProgress | { task: Task; error: string }>,
         ) => {
             if (socket.readyState === socket.OPEN) {
-                socket.send(JSON.stringify({ type: e.type, detail: e.detail }));
+                socket.send(toJSON({ type: e.type, detail: e.detail }));
             }
         };
         const close_handle = () => {
@@ -42,7 +43,7 @@ export const handler: Handlers = {
         };
         function sendMessage(mes: TaskServerSocketData) {
             if (socket.readyState === socket.OPEN) {
-                socket.send(JSON.stringify(mes));
+                socket.send(toJSON(mes));
             }
         }
         const interval = setInterval(() => {
diff --git a/server/utils.ts b/server/utils.ts
index eecbc07..0aec2c0 100644
--- a/server/utils.ts
+++ b/server/utils.ts
@@ -1,3 +1,5 @@
+import { toJSON } from "../utils.ts";
+
 export function get_ws_host() {
     const protocol = document.location.protocol === "https:" ? "wss:" : "ws:";
     return `${protocol}//${document.location.host}`;
@@ -23,7 +25,7 @@ function gen_response<T>(
     }
     const h = new Headers(headers);
     h.set("Content-Type", "application/json; charset=UTF-8");
-    return new Response(JSON.stringify(d), { status, headers: h });
+    return new Response(toJSON(d), { status, headers: h });
 }
 
 export function return_error<T = unknown>(
@@ -55,7 +57,7 @@ export function gen_error<T = unknown>(
 }
 
 export function return_json<T = unknown>(data: T, status = 200) {
-    return new Response(JSON.stringify(data), {
+    return new Response(toJSON(data), {
         status,
         headers: { "Content-Type": "application/json; chatset=UTF-8" },
     });
diff --git a/task_manager.ts b/task_manager.ts
index 2d916f0..ab816c5 100644
--- a/task_manager.ts
+++ b/task_manager.ts
@@ -23,6 +23,7 @@ import {
     PromiseStatus,
     RecoverableError,
     sleep,
+    toJSON,
 } from "./utils.ts";
 
 export class AlreadyClosedError extends Error {
@@ -124,7 +125,7 @@ export class TaskManager extends EventTarget {
             id: 0,
             pid: Deno.pid,
             type: TaskType.Download,
-            details: cfg ? JSON.stringify(cfg) : null,
+            details: cfg ? toJSON(cfg) : null,
         };
         return await this.#add_task(task);
     }
@@ -135,7 +136,7 @@ export class TaskManager extends EventTarget {
             id: 0,
             pid: Deno.pid,
             type: TaskType.ExportZip,
-            details: JSON.stringify(cfg || DEFAULT_EXPORT_ZIP_CONFIG),
+            details: toJSON(cfg || DEFAULT_EXPORT_ZIP_CONFIG),
         };
         return await this.#add_task(task);
     }
diff --git a/utils.ts b/utils.ts
index 1d9d4d5..235dc26 100644
--- a/utils.ts
+++ b/utils.ts
@@ -281,3 +281,11 @@ export function isDocker() {
     }
     return _isDocker;
 }
+
+export function toJSON(obj: unknown) {
+    return JSON.stringify(
+        obj,
+        (_, value) =>
+            typeof value === "bigint" ? parseInt(value.toString()) : value,
+    );
+}
diff --git a/utils_test.ts b/utils_test.ts
index 017f139..eeef861 100644
--- a/utils_test.ts
+++ b/utils_test.ts
@@ -12,6 +12,7 @@ import {
     PromiseStatus,
     sleep,
     sure_dir,
+    toJSON,
 } from "./utils.ts";
 import { md5 } from "lifegpc-md5";
 
@@ -158,3 +159,11 @@ Deno.test("map_test", () => {
     }, d);
     assertEquals(re, [3, 4]);
 });
+
+Deno.test("toJSON_test", () => {
+    assertEquals(toJSON({ a: 3n }), '{"a":3}');
+    assertEquals(
+        toJSON([1099511627776n, { a: 45n }]),
+        '[1099511627776,{"a":45}]',
+    );
+});