# Chats vs Channels

Telegram’s raw API can get very confusing sometimes, in particular when it comes to talking about “chats”, “channels”, “groups”, “megagroups”, and all those concepts.

This section will try to explain what each of these concepts are.

## Chats

A `Chat` can be used to talk about either the common “subclass” that both chats and channels share, or the concrete Chat type.

Technically, both Chat and Channel are a form of the Chat type.

Most of the time, the term Chat is used to talk about small group chats. When you create a group through an official application, this is the type that you get. Official applications refer to these as “Group”.

Both the bot API and Telethon will add a minus sign (negate) the real chat ID so that you can tell at a glance, with just a number, the entity type.

For example, if you create a chat with CreateChatRequest, the real chat ID might be something like `123`. If you try printing it from a `message.chat_id` you will see `-123`. This ID helps Telethon know you’re talking about a Chat.

## Channels

Official applications create a broadcast channel when you create a new channel (used to broadcast messages, only administrators can post messages).

Official applications implicitly migrate an existing Chat to a megagroup Channel when you perform certain actions (exceed user limit, add a public username, set certain permissions, etc.).

A `Channel` can be created directly with CreateChannelRequest, as either a `megagroup` or `broadcast`.

Official applications use the term “channel” only for broadcast channels.

The API refers to the different types of Channel with certain attributes:

- A broadcast channel is a Channel with the `channel.broadcast` attribute set to `True`.

- A megagroup channel is a Channel with the `channel.megagroup` attribute set to `True`. Official applications refer to this as “supergroup”.

- A gigagroup channel is a Channel with the `channel.gigagroup` attribute set to `True`. Official applications refer to this as “broadcast groups”, and is used when a megagroup becomes very large and administrators want to transform it into something where only they can post messages.

Both the bot API and Telethon will “concatenate” `-100` to the real chat ID so that you can tell at a glance, with just a number, the entity type.

For example, if you create a new broadcast channel, the real channel ID might be something like `456`. If you try printing it from a `message.chat_id` you will see `-1000000000456`. This ID helps Telethon know you’re talking about a Channel.

## Converting IDs

You can convert between the “marked” identifiers (prefixed with a minus sign) and the real ones with `utils.resolve_id`. It will return a tuple with the real ID, and the peer type (the class):

    from telethon import utils
    real_id, peer_type = utils.resolve_id(-1000000000456)

    print(real_id)  # 456
    print(peer_type)  # <class 'telethon.tl.types.PeerChannel'>

    peer = peer_type(real_id)
    print(peer)  # PeerChannel(channel_id=456)

The reverse operation can be done with `utils.get_peer_id`:

    print(utils.get_peer_id(types.PeerChannel(456)))  # -1000000000456

Note that this function can also work with other types, like Chat or Channel instances.

If you need to convert other types like usernames which might need to perform API calls to find out the identifier, you can use `client.get_peer_id`:

    print(await client.get_peer_id('me'))  # your id

If there is no “mark” (no minus sign), Telethon will assume your identifier refers to a User. If this is not the case, you can manually fix it:

    from telethon import types
    await client.send_message(types.PeerChannel(456), 'hello')
    #                         ^^^^^^^^^^^^^^^^^ explicit peer type

## A note on raw API

Certain methods only work on a Chat, and some others only work on a Channel (and these may only work in broadcast, or megagroup). Your code likely knows what it’s working with, so it shouldn’t be too much of an issue.

If you need to find the Channel from a Chat that migrated to it, access the `migrated_to` property:

    # chat is a Chat
    channel = await client.get_entity(chat.migrated_to)
    # channel is now a Channel

Channels do not have a “migrated_from”, but a ChannelFull does. You can use GetFullChannelRequest to obtain this:

    from telethon import functions
    full = await client(functions.channels.GetFullChannelRequest(your_channel))
    full_channel = full.full_chat
    # full_channel is a ChannelFull
    print(full_channel.migrated_from_chat_id)

This way, you can also access the linked discussion megagroup of a broadcast channel:

    print(full_channel.linked_chat_id)  # prints ID of linked discussion group or None

You do not need to use `client.get_entity` to access the `migrated_from_chat_id` Chat or the `linked_chat_id` Channel. They are in the `full.chats` attribute:

    if full_channel.migrated_from_chat_id:
        migrated_from_chat = next(c for c in full.chats if c.id == full_channel.migrated_from_chat_id)
        print(migrated_from_chat.title)

    if full_channel.linked_chat_id:
        linked_group = next(c for c in full.chats if c.id == full_channel.linked_chat_id)
        print(linked_group.username)