diff --git a/packages/frontend-embed/src/custom-emojis.ts b/packages/frontend-embed/src/custom-emojis.ts
new file mode 100644
index 0000000000..0c402da2c0
--- /dev/null
+++ b/packages/frontend-embed/src/custom-emojis.ts
@@ -0,0 +1,61 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and misskey-project
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import { shallowRef, computed, markRaw, watch } from 'vue';
+import * as Misskey from 'misskey-js';
+import { misskeyApi, misskeyApiGet } from '@/scripts/misskey-api.js';
+import { get, set } from '@/scripts/idb-proxy.js';
+
+const storageCache = await get('emojis');
+export const customEmojis = shallowRef<Misskey.entities.EmojiSimple[]>(Array.isArray(storageCache) ? storageCache : []);
+export const customEmojiCategories = computed<[ ...string[], null ]>(() => {
+	const categories = new Set<string>();
+	for (const emoji of customEmojis.value) {
+		if (emoji.category && emoji.category !== 'null') {
+			categories.add(emoji.category);
+		}
+	}
+	return markRaw([...Array.from(categories), null]);
+});
+
+export const customEmojisMap = new Map<string, Misskey.entities.EmojiSimple>();
+watch(customEmojis, emojis => {
+	customEmojisMap.clear();
+	for (const emoji of emojis) {
+		customEmojisMap.set(emoji.name, emoji);
+	}
+}, { immediate: true });
+
+export async function fetchCustomEmojis(force = false) {
+	const now = Date.now();
+
+	let res;
+	if (force) {
+		res = await misskeyApi('emojis', {});
+	} else {
+		const lastFetchedAt = await get('lastEmojisFetchedAt');
+		if (lastFetchedAt && (now - lastFetchedAt) < 1000 * 60 * 60) return;
+		res = await misskeyApiGet('emojis', {});
+	}
+
+	customEmojis.value = res.emojis;
+	set('emojis', res.emojis);
+	set('lastEmojisFetchedAt', now);
+}
+
+let cachedTags;
+export function getCustomEmojiTags() {
+	if (cachedTags) return cachedTags;
+
+	const tags = new Set();
+	for (const emoji of customEmojis.value) {
+		for (const tag of emoji.aliases) {
+			tags.add(tag);
+		}
+	}
+	const res = Array.from(tags);
+	cachedTags = res;
+	return res;
+}
diff --git a/packages/frontend-embed/src/misskey-api.ts b/packages/frontend-embed/src/misskey-api.ts
new file mode 100644
index 0000000000..13630590b6
--- /dev/null
+++ b/packages/frontend-embed/src/misskey-api.ts
@@ -0,0 +1,99 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and misskey-project
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import * as Misskey from 'misskey-js';
+import { ref } from 'vue';
+import { apiUrl } from '@/config.js';
+
+export const pendingApiRequestsCount = ref(0);
+
+// Implements Misskey.api.ApiClient.request
+export function misskeyApi<
+	ResT = void,
+	E extends keyof Misskey.Endpoints = keyof Misskey.Endpoints,
+	P extends Misskey.Endpoints[E]['req'] = Misskey.Endpoints[E]['req'],
+	_ResT = ResT extends void ? Misskey.api.SwitchCaseResponseType<E, P> : ResT,
+>(
+	endpoint: E,
+	data: P = {} as any,
+	signal?: AbortSignal,
+): Promise<_ResT> {
+	if (endpoint.includes('://')) throw new Error('invalid endpoint');
+	pendingApiRequestsCount.value++;
+
+	const onFinally = () => {
+		pendingApiRequestsCount.value--;
+	};
+
+	const promise = new Promise<_ResT>((resolve, reject) => {
+		// Send request
+		window.fetch(`${apiUrl}/${endpoint}`, {
+			method: 'POST',
+			body: JSON.stringify(data),
+			credentials: 'omit',
+			cache: 'no-cache',
+			headers: {
+				'Content-Type': 'application/json',
+			},
+			signal,
+		}).then(async (res) => {
+			const body = res.status === 204 ? null : await res.json();
+
+			if (res.status === 200) {
+				resolve(body);
+			} else if (res.status === 204) {
+				resolve(undefined as _ResT); // void -> undefined
+			} else {
+				reject(body.error);
+			}
+		}).catch(reject);
+	});
+
+	promise.then(onFinally, onFinally);
+
+	return promise;
+}
+
+// Implements Misskey.api.ApiClient.request
+export function misskeyApiGet<
+	ResT = void,
+	E extends keyof Misskey.Endpoints = keyof Misskey.Endpoints,
+	P extends Misskey.Endpoints[E]['req'] = Misskey.Endpoints[E]['req'],
+	_ResT = ResT extends void ? Misskey.api.SwitchCaseResponseType<E, P> : ResT,
+>(
+	endpoint: E,
+	data: P = {} as any,
+): Promise<_ResT> {
+	pendingApiRequestsCount.value++;
+
+	const onFinally = () => {
+		pendingApiRequestsCount.value--;
+	};
+
+	const query = new URLSearchParams(data as any);
+
+	const promise = new Promise<_ResT>((resolve, reject) => {
+		// Send request
+		window.fetch(`${apiUrl}/${endpoint}?${query}`, {
+			method: 'GET',
+			credentials: 'omit',
+			cache: 'default',
+		}).then(async (res) => {
+			const body = res.status === 204 ? null : await res.json();
+
+			if (res.status === 200) {
+				resolve(body);
+			} else if (res.status === 204) {
+				resolve(undefined as _ResT); // void -> undefined
+			} else {
+				reject(body.error);
+			}
+		}).catch(reject);
+	});
+
+	promise.then(onFinally, onFinally);
+
+	return promise;
+}