Aiogram: How to automatically detect when bot joins a new group and capture the group ID?

[SpinningGalaxy]

I’m working on a bot that forwards photos from private messages to all groups where it has admin rights. Right now I have to manually add group IDs to my list, but I want to automate this process.

my_bot = Bot(token=BOT_TOKEN)
dispatcher = Dispatcher()
group_list = []

async def verify_admin_status(group_id):
    chat_member = await my_bot.get_chat_member(group_id, my_bot.id)
    status = chat_member.status
    return status

@dispatcher.message(F.photo)
async def process_image(msg: types.Message):
    for target_group in group_list:
        admin_check = await verify_admin_status(target_group)
        if msg.chat.type == 'private' and admin_check:
            await msg.copy_to(chat_id=target_group)

async def start_bot():
    await dispatcher.start_polling(my_bot)

The bot works fine for forwarding images, but I need to populate the group_list manually. Is there a way to automatically catch when someone adds my bot to a group and store that group’s ID? I want the bot to automatically know about all groups it belongs to without manual configuration.

[alexlee]

You need to handle ChatMemberUpdated events to track when your bot joins new groups. The previous answer got the handler right, but here’s a more complete approach:

@dispatcher.chat_member()
async def track_bot_membership(update: types.ChatMemberUpdated):
    if update.new_chat_member.user.id == my_bot.id:
        if update.new_chat_member.status in ['member', 'administrator']:
            group_id = update.chat.id
            if group_id not in group_list:
                group_list.append(group_id)
                print(f"Bot added to group: {group_id}")
        elif update.new_chat_member.status == 'left':
            if update.chat.id in group_list:
                group_list.remove(update.chat.id)

This handles both joining and leaving groups automatically. Just make sure you save the group_list to a file or database so it survives bot restarts - otherwise you’ll lose all the group IDs every time you restart.

[CreativeArtist88]

use the my_chat_member handler to catch when ur bot gets added to groups. add @dispatcher.my_chat_member() and check if update.new_chat_member.status is member or admin. if it is, save the chat id to ur list automatically.

[mikezhang]

Both answers are right about chat member handlers, but here’s a gotcha that bit me hard. When your bot starts up, it won’t know about groups it’s already in - these handlers only catch new events, not existing memberships. You’ll need a startup check that queries your bot’s existing group memberships using get_updates with a filter, or just maintain persistent storage from day one. Also, some groups restrict member addition notifications, so the handler might not fire every time. I’d combine the automatic detection with a manual fallback command that admins can use to register their groups when the automatic method fails.