Init Data

When a Mini App launches, the client passes a signed initialization data string through Telegram.WebApp.initData. This string contains information about the user, chat, and launch parameters.

Telegram.WebApp.initDataUnsafe provides the parsed WebAppInitData object for convenient client-side access.

Security Notice

Data in initDataUnsafe has not been server-side verified and should only be used for client-side display. Business-critical data must be verified on the server using the raw initData string through signature validation.

WebAppInitData

Initialization data object, accessed via Telegram.WebApp.initDataUnsafe.

Field	Type	Description
query_id	String	Unique query ID for answerWebAppQuery
user	WebAppUser	Current user information
receiver	WebAppUser	Other user in the conversation (only available in private chats)
chat	WebAppChat	Current chat information (only available in groups/channels)
chat_type	String	Chat type: "sender", "private", "group", "supergroup", "channel"
chat_instance	String	Unique identifier of the chat instance
start_param	String	Start parameter passed via link
can_send_after	Integer	Earliest time to call sendData (Unix timestamp)
auth_date	Integer	Authentication time (Unix timestamp)
hash	String	Data signature hash for verification
signature	String	Data signature for third-party verification. Bot API 8.0+

WebAppUser

User information object.

Field	Type	Description
id	Integer	User ID
is_bot	Boolean	Whether the user is a bot
first_name	String	First name
last_name	String	Last name (optional)
username	String	Username (optional)
language_code	String	User language code (e.g., "zh-hans", "en")
is_premium	Boolean	Whether the user is a Premium user (optional)
added_to_attachment_menu	Boolean	Whether the user has added the bot to attachment menu (optional)
allows_write_to_pm	Boolean	Whether the user allows the bot to send private messages (optional)
photo_url	String	User avatar URL (optional)

WebAppChat

Chat information object.

Field	Type	Description
id	Integer	Chat ID
type	String	Chat type: "group", "supergroup", "channel"
title	String	Chat title
username	String	Chat username (optional)
photo_url	String	Chat avatar URL (optional)

Usage Example

const tg = Telegram.WebApp;
const initData = tg.initDataUnsafe;

// Get user info
if (initData.user) {
  console.log('User ID:', initData.user.id);
  console.log('Name:', initData.user.first_name);
  console.log('Language:', initData.user.language_code);
  console.log('Premium:', initData.user.is_premium);
}

// Get chat info
if (initData.chat) {
  console.log('Chat ID:', initData.chat.id);
  console.log('Chat title:', initData.chat.title);
}

// Get start parameter
if (initData.start_param) {
  console.log('Start param:', initData.start_param);
  handleStartParam(initData.start_param);
}

// Send raw data to server for validation
fetch('/api/auth', {
  method: 'POST',
  headers: { 'Content-Type': 'application/json' },
  body: JSON.stringify({ initData: tg.initData })
});

initData Query String Format

Telegram.WebApp.initData is a URL-encoded query string containing the following parameters:

query_id=AAHd...&user=%7B%22id%22%3A123...%7D&auth_date=1234567890&hash=abc123...

When parsed, it contains the following key-value pairs:

Key	Value
query_id	Query ID string
user	JSON-encoded user object
receiver	JSON-encoded receiver object
chat	JSON-encoded chat object
chat_type	Chat type string
chat_instance	Chat instance ID
start_param	Start parameter
can_send_after	Allowed send timestamp
auth_date	Authentication timestamp
hash	HMAC-SHA256 signature
signature	Ed25519 signature

For detailed validation methods, see Data Validation.