diff --git a/packages/client/src/index.ts b/packages/client/src/index.ts
index 7c9237be..bf786a73 100644
--- a/packages/client/src/index.ts
+++ b/packages/client/src/index.ts
@@ -4,6 +4,7 @@ export {
     LocalstorageStorage,
     tl,
     defaultDcs,
+    assertNever,
 } from '@mtcute/core'
 
 export * from './types'
diff --git a/packages/i18n/README.md b/packages/i18n/README.md
new file mode 100644
index 00000000..51392cc8
--- /dev/null
+++ b/packages/i18n/README.md
@@ -0,0 +1,7 @@
+# @mtcute/i18n
+
+> I18n for MTCute
+
+This package implements utility for i18n functionality in `@mtcute/client` based apps.
+
+Documentation is TBA.
diff --git a/packages/i18n/package.json b/packages/i18n/package.json
new file mode 100644
index 00000000..22b3478e
--- /dev/null
+++ b/packages/i18n/package.json
@@ -0,0 +1,18 @@
+{
+    "name": "@mtcute/i18n",
+    "private": true,
+    "version": "1.0.0",
+    "description": "I18n for MTCute",
+    "author": "Alisa Sireneva <me@tei.su>",
+    "license": "LGPL-3.0",
+    "main": "src/index.ts",
+    "scripts": {
+        "test": "mocha -r ts-node/register \"tests/**/*.spec.ts\"",
+        "coverage": "nyc npm run test",
+        "build": "tsc",
+        "docs": "npx typedoc"
+    },
+    "dependencies": {
+        "@mtcute/client": "workspace:^1.0.0"
+    }
+}
diff --git a/packages/i18n/src/index.ts b/packages/i18n/src/index.ts
new file mode 100644
index 00000000..bf379210
--- /dev/null
+++ b/packages/i18n/src/index.ts
@@ -0,0 +1,74 @@
+import { MtArgumentError, ParsedUpdate } from '@mtcute/client'
+import { I18nValue, MtcuteI18nFunction, OtherLanguageWrap } from './types'
+import { createI18nStringsIndex, extractLanguageFromUpdate } from './utils'
+
+export interface MtcuteI18nParameters<Strings> {
+    /**
+     * Primary language which will also be used as a fallback
+     */
+    primaryLanguage: {
+        /**
+         * Two letter language code.
+         */
+        name: string
+
+        /**
+         * Strings for the language.
+         */
+        strings: Strings
+    }
+
+    otherLanguages?: Record<string, OtherLanguageWrap<Strings>>
+
+    /**
+     * Language that will be used if no language is specified
+     *
+     * Defaults to {@link primaryLanguage}
+     */
+    defaultLanguage?: string
+}
+
+export function createMtcuteI18n<Strings>(
+    params: MtcuteI18nParameters<Strings>
+): MtcuteI18nFunction<Strings> {
+    const {
+        primaryLanguage,
+        otherLanguages,
+        defaultLanguage = primaryLanguage.name,
+    } = params
+
+    const indexes: Record<string, Record<string, I18nValue>> = {}
+    const fallbackIndex = (indexes[primaryLanguage.name] =
+        createI18nStringsIndex(primaryLanguage.strings))
+    if (otherLanguages) {
+        Object.keys(otherLanguages).forEach((lang) => {
+            indexes[lang] = createI18nStringsIndex(otherLanguages[lang])
+        })
+    }
+
+    if (!(defaultLanguage in indexes)) {
+        throw new MtArgumentError(
+            'defaultLanguage is not a registered language'
+        )
+    }
+
+    const tr = (lang: ParsedUpdate['data'] | string | null, key: string, ...params: any[]) => {
+        if (lang === null) lang = defaultLanguage
+
+        if (typeof lang === 'object') {
+            lang = extractLanguageFromUpdate(lang) ?? defaultLanguage
+        }
+
+        const strings = indexes[lang] ?? fallbackIndex
+
+        let val = strings[key] ?? fallbackIndex[key] ?? `[missing: ${key}]`
+
+        if (typeof val === 'function') {
+            val = val(...params)
+        }
+
+        return val
+    }
+
+    return tr as MtcuteI18nFunction<Strings>
+}
diff --git a/packages/i18n/src/types.ts b/packages/i18n/src/types.ts
new file mode 100644
index 00000000..eb19c394
--- /dev/null
+++ b/packages/i18n/src/types.ts
@@ -0,0 +1,39 @@
+import { ParsedUpdate } from '@mtcute/client'
+
+type Values<T> = T[keyof T]
+type SafeGet<T, K extends string> = T extends Record<K, any> ? T[K] : never
+
+export type I18nValue = string | ((...args: any[]) => string)
+
+type NestedKeysDelimited<T> = Values<{
+    [key in Extract<keyof T, string>]: T[key] extends I18nValue
+        ? key
+        : `${key}.${T[key] extends infer R ? NestedKeysDelimited<R> : never}`
+}>
+
+type GetValueNested<T, K extends string> = K extends `${infer P}.${infer Q}`
+    ? GetValueNested<SafeGet<T, P>, Q>
+    : SafeGet<T, K>
+
+type ExtractParameter<Strings, K extends string> = GetValueNested<
+    Strings,
+    K
+> extends (...params: infer R) => any
+    ? R
+    : never
+
+export type MtcuteI18nFunction<Strings> = <
+    K extends NestedKeysDelimited<Strings>
+>(
+    lang: ParsedUpdate['data'] | string | null,
+    key: K,
+    ...params: ExtractParameter<Strings, K>
+) => string
+
+export type OtherLanguageWrap<Strings> = {
+    [key in keyof Strings]?: Strings[key] extends I18nValue
+        ? I18nValue
+        : Strings[key] extends Record<string, any>
+        ? OtherLanguageWrap<Strings[key]>
+        : never
+}
diff --git a/packages/i18n/src/utils.ts b/packages/i18n/src/utils.ts
new file mode 100644
index 00000000..49f53216
--- /dev/null
+++ b/packages/i18n/src/utils.ts
@@ -0,0 +1,68 @@
+import {
+    ParsedUpdate,
+    assertNever,
+    User,
+    Message,
+    DeleteMessageUpdate,
+    ChatMemberUpdate,
+    InlineQuery,
+    ChosenInlineResult,
+    CallbackQuery,
+    PollUpdate,
+    PollVoteUpdate,
+    UserStatusUpdate,
+    BotStoppedUpdate,
+    BotChatJoinRequestUpdate,
+} from '@mtcute/client'
+import { I18nValue } from './types'
+
+export function createI18nStringsIndex(
+    strings: Record<string, any>
+): Record<string, I18nValue> {
+    const ret: Record<string, I18nValue> = {}
+
+    function add(obj: Record<string, any>, prefix: string) {
+        for (const key in obj) {
+            const val = obj[key]
+
+            if (typeof val === 'object') {
+                add(val, prefix + key + '.')
+            } else {
+                ret[prefix + key] = val
+            }
+        }
+    }
+
+    add(strings, '')
+
+    return ret
+}
+
+export function extractLanguageFromUpdate(
+    update: ParsedUpdate['data']
+): string | null | undefined {
+    switch (update.constructor) {
+        case Message:
+            // if sender is Chat it will just be undefined
+            return ((update as Message).sender as User).language
+        case ChatMemberUpdate:
+        case InlineQuery:
+        case ChosenInlineResult:
+        case CallbackQuery:
+        case PollVoteUpdate:
+        case BotStoppedUpdate:
+        case BotChatJoinRequestUpdate:
+            return (
+                update as
+                    | ChatMemberUpdate
+                    | InlineQuery
+                    | ChosenInlineResult
+                    | CallbackQuery
+                    | PollVoteUpdate
+                    | BotStoppedUpdate
+                    | BotChatJoinRequestUpdate
+            ).user.language
+    }
+
+    return null
+}
diff --git a/packages/i18n/tests/i18n.spec.ts b/packages/i18n/tests/i18n.spec.ts
new file mode 100644
index 00000000..c328f759
--- /dev/null
+++ b/packages/i18n/tests/i18n.spec.ts
@@ -0,0 +1,94 @@
+import { describe, it } from 'mocha'
+import { expect } from 'chai'
+import { createMtcuteI18n } from '../src'
+import { OtherLanguageWrap } from '../src/types'
+import { Message, PeersIndex } from '@mtcute/client'
+
+describe('i18n', () => {
+    const en = {
+        direct: 'Hello',
+        fn: () => 'World',
+        withArgs: (name: string) => `Welcome ${name}`,
+        withArgsObj: ({ name }: { name: string }) => `Welcome ${name}`,
+        nested: {
+            string: 'Hello',
+            nested: {
+                fn: () => 'Hello',
+            },
+        },
+    }
+    const ru: OtherLanguageWrap<typeof en> = {
+        direct: 'Привет',
+        // fn: () => 'World',
+        withArgs: (name: string) => `Привет ${name}`,
+        // withArgsObj: ({ name }: { name: string }) => `Welcome ${name}`,
+        nested: {
+            // string: 'Hello',
+            nested: {
+                fn: 'Привет',
+            },
+        },
+    }
+
+    const tr = createMtcuteI18n({
+        primaryLanguage: {
+            name: 'en',
+            strings: en,
+        },
+        otherLanguages: { ru },
+    })
+
+    it('should work with direct string', () => {
+        expect(tr('en', 'direct')).to.equal('Hello')
+    })
+
+    it('should work with function without args', () => {
+        expect(tr('en', 'fn')).to.equal('World')
+    })
+
+    it('should work with function with args', () => {
+        expect(tr('en', 'withArgs', '')).to.equal('Welcome ')
+        expect(tr('en', 'withArgs', 'John')).to.equal('Welcome John')
+        expect(tr('en', 'withArgsObj', { name: 'John' })).to.equal(
+            'Welcome John'
+        )
+    })
+
+    it('should work with nested values', () => {
+        expect(tr('en', 'nested.string')).to.equal('Hello')
+        expect(tr('en', 'nested.nested.fn')).to.equal('Hello')
+    })
+
+    it('should work with other languages', () => {
+        expect(tr('ru', 'direct')).to.equal('Привет')
+        expect(tr('ru', 'withArgs', 'Ваня')).to.equal('Привет Ваня')
+        expect(tr('ru', 'nested.nested.fn')).to.equal('Привет')
+    })
+
+    it('should fallback to primary language when string is not translated', () => {
+        expect(tr('ru', 'fn')).to.equal('World')
+        expect(tr('ru', 'withArgsObj', { name: 'Ваня' })).to.equal(
+            'Welcome Ваня'
+        )
+        expect(tr('ru', 'nested.string')).to.equal('Hello')
+    })
+
+    it('should fallback to primary language when language is not available', () => {
+        expect(tr('kz', 'direct')).to.equal('Hello')
+        expect(tr(null, 'direct')).to.equal('Hello')
+    })
+
+    it('should parse language from a message', () => {
+        const message = new Message(
+            null as any,
+            { _: 'message', peerId: { _: 'peerUser', userId: 1 } } as any,
+            PeersIndex.from({
+                users: [
+                    { _: 'user', id: 1, firstName: 'Пыня', langCode: 'ru' },
+                ],
+            })
+        )
+
+        expect(tr(message, 'direct')).to.equal('Привет')
+    })
+})
diff --git a/packages/i18n/tests/types.ts b/packages/i18n/tests/types.ts
new file mode 100644
index 00000000..3e1eb4d2
--- /dev/null
+++ b/packages/i18n/tests/types.ts
@@ -0,0 +1,37 @@
+/* eslint-disable */
+// This is a test for TypeScript typings
+// This file is never executed, only compiled
+
+import { Message } from '@mtcute/client'
+import { createMtcuteI18n } from '../src'
+import { OtherLanguageWrap } from '../src/types'
+
+const en = {
+    basic: {
+        hello: 'Hello',
+        world: () => 'World',
+        welcome: (name: string) => `Welcome ${name}`,
+    },
+}
+
+const ru: OtherLanguageWrap<typeof en> = {
+    basic: {
+        hello: 'Привет',
+        // world: () => 'Мир',
+        welcome: (name: string) => `Привет ${name}`,
+    },
+}
+
+const tr = createMtcuteI18n({
+    primaryLanguage: {
+        name: 'en',
+        strings: en,
+    },
+    otherLanguages: { ru },
+})
+
+declare const ref: Message
+
+const a = tr(ref, 'basic.hello')
+const b = tr('ru', 'basic.world') // will fallback to en
+const c = tr(null, 'basic.welcome', 'John')
diff --git a/packages/i18n/tsconfig.json b/packages/i18n/tsconfig.json
new file mode 100644
index 00000000..6a8fe885
--- /dev/null
+++ b/packages/i18n/tsconfig.json
@@ -0,0 +1,19 @@
+{
+    "extends": "../../tsconfig.json",
+    "compilerOptions": {
+        "outDir": "./dist"
+    },
+    "include": [
+        "./src"
+    ],
+    "typedocOptions": {
+        "name": "@mtcute/html-parser",
+        "includeVersion": true,
+        "out": "../../docs/packages/html-parser",
+        "listInvalidSymbolLinks": true,
+        "excludePrivate": true,
+        "entryPoints": [
+            "./src/index.ts"
+        ]
+    }
+}
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index 749dd8d9..70998586 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -1,4 +1,4 @@
-lockfileVersion: 5.4
+lockfileVersion: 5.3
 
 importers:
 
@@ -34,8 +34,8 @@ importers:
       '@types/node': 14.18.16
       '@types/node-forge': 1.0.2
       '@types/ws': 7.4.7
-      '@typescript-eslint/eslint-plugin': 4.33.0_3ekaj7j3owlolnuhj3ykrb7u7i
-      '@typescript-eslint/parser': 4.33.0_hxadhbs2xogijvk7vq4t2azzbu
+      '@typescript-eslint/eslint-plugin': 4.33.0_d91404fd3b7596e5b6874ef0a887f4fa
+      '@typescript-eslint/parser': 4.33.0_eslint@7.32.0+typescript@4.7.4
       chai: 4.3.6
       dotenv-flow: 3.2.0
       eslint: 7.32.0
@@ -47,7 +47,7 @@ importers:
       prettier: 2.6.2
       rimraf: 3.0.2
       semver: 7.3.7
-      ts-node: 10.8.1_n4ne3vfoqubxgiypogr36fpdje
+      ts-node: 10.8.1_6f1a4dd4ae850373230f71a3bf15e349
       typedoc: 0.23.2_typescript@4.7.4
       typescript: 4.7.4
 
@@ -153,6 +153,12 @@ importers:
     dependencies:
       '@mtcute/core': link:../core
 
+  packages/i18n:
+    specifiers:
+      '@mtcute/client': workspace:^1.0.0
+    devDependencies:
+      '@mtcute/client': link:../client
+
   packages/markdown-parser:
     specifiers:
       '@mtcute/client': workspace:^1.0.0
@@ -691,7 +697,7 @@ packages:
       '@types/node': 14.18.16
     dev: true
 
-  /@typescript-eslint/eslint-plugin/4.33.0_3ekaj7j3owlolnuhj3ykrb7u7i:
+  /@typescript-eslint/eslint-plugin/4.33.0_d91404fd3b7596e5b6874ef0a887f4fa:
     resolution: {integrity: sha512-aINiAxGVdOl1eJyVjaWn/YcVAq4Gi/Yo35qHGCnqbWVz61g39D0h23veY/MA0rFFGfxK7TySg2uwDeNv+JgVpg==}
     engines: {node: ^10.12.0 || >=12.0.0}
     peerDependencies:
@@ -702,8 +708,8 @@ packages:
       typescript:
         optional: true
     dependencies:
-      '@typescript-eslint/experimental-utils': 4.33.0_hxadhbs2xogijvk7vq4t2azzbu
-      '@typescript-eslint/parser': 4.33.0_hxadhbs2xogijvk7vq4t2azzbu
+      '@typescript-eslint/experimental-utils': 4.33.0_eslint@7.32.0+typescript@4.7.4
+      '@typescript-eslint/parser': 4.33.0_eslint@7.32.0+typescript@4.7.4
       '@typescript-eslint/scope-manager': 4.33.0
       debug: 4.3.4
       eslint: 7.32.0
@@ -717,7 +723,7 @@ packages:
       - supports-color
     dev: true
 
-  /@typescript-eslint/experimental-utils/4.33.0_hxadhbs2xogijvk7vq4t2azzbu:
+  /@typescript-eslint/experimental-utils/4.33.0_eslint@7.32.0+typescript@4.7.4:
     resolution: {integrity: sha512-zeQjOoES5JFjTnAhI5QY7ZviczMzDptls15GFsI6jyUOq0kOf9+WonkhtlIhh0RgHRnqj5gdNxW5j1EvAyYg6Q==}
     engines: {node: ^10.12.0 || >=12.0.0}
     peerDependencies:
@@ -735,7 +741,7 @@ packages:
       - typescript
     dev: true
 
-  /@typescript-eslint/parser/4.33.0_hxadhbs2xogijvk7vq4t2azzbu:
+  /@typescript-eslint/parser/4.33.0_eslint@7.32.0+typescript@4.7.4:
     resolution: {integrity: sha512-ZohdsbXadjGBSK0/r+d87X0SBmKzOq4/S5nzK6SBgJspFo9/CUDJ7hjayuze+JK7CZQLDMroqytp7pOcFKTxZA==}
     engines: {node: ^10.12.0 || >=12.0.0}
     peerDependencies:
@@ -1083,8 +1089,6 @@ packages:
       ssri: 9.0.0
       tar: 6.1.11
       unique-filename: 1.1.1
-    transitivePeerDependencies:
-      - bluebird
     dev: false
 
   /caching-transform/4.0.0:
@@ -2353,7 +2357,6 @@ packages:
       socks-proxy-agent: 6.2.0
       ssri: 9.0.0
     transitivePeerDependencies:
-      - bluebird
       - supports-color
     dev: false
 
@@ -2581,7 +2584,6 @@ packages:
       tar: 6.1.11
       which: 2.0.2
     transitivePeerDependencies:
-      - bluebird
       - supports-color
     dev: false
 
@@ -2874,11 +2876,6 @@ packages:
 
   /promise-inflight/1.0.1:
     resolution: {integrity: sha1-mEcocL8igTL8vdhoEputEsPAKeM=}
-    peerDependencies:
-      bluebird: '*'
-    peerDependenciesMeta:
-      bluebird:
-        optional: true
     dev: false
 
   /promise-retry/2.0.1:
@@ -3318,7 +3315,7 @@ packages:
     resolution: {integrity: sha1-gYT9NH2snNwYWZLzpmIuFLnZq2o=}
     dev: true
 
-  /ts-node/10.8.1_n4ne3vfoqubxgiypogr36fpdje:
+  /ts-node/10.8.1_6f1a4dd4ae850373230f71a3bf15e349:
     resolution: {integrity: sha512-Wwsnao4DQoJsN034wePSg5nZiw4YKXf56mPIAeD6wVmiv+RytNSWqc2f3fKvcUoV+Yn2+yocD71VOfQHbmVX4g==}
     hasBin: true
     peerDependencies: