When you post a message on a Channel, there are a few things that happen on the server:

1. The text markdown format is parsed.
2. The first URL found in message.text is enriched, and additional information is added automatically. This gives you a preview of the images, videos, etc. from the open-graph data on the associated page.

Any slash commands such as /giphy, /ban, /flag, etc. are handled.

Messages containing URLs will have a generated attachment with the following structure:

name	type	description	default	optional
type	string	The attachment type based on the URL resource. This can be: audio, image or video		✓
author_name	string	The name of the author.		✓
title	string	The attachment title.		✓
title_link	string	The link to which the attachment message points to.		✓
text	string	The attachment text. It will be displayed in the channel next to the original message.		✓
image_url	string	The URL to the attached image. This is present for URL pointing to an image article (eg. Unsplash)		✓
thumb_url	string	The URL to the attached file thumbnail. You can use this to represent the attached link.		✓
asset_url	string	The URL to the audio, video or image related to the URL.		✓
og_scrape_url	string	The original URL that was used to scrape this attachment.		✓

Our scraper uses the following user agent, as well as the latest desktop and mobile user agents: getstream.io/opengraph-bot facebookexternalhit/1.1 (+http://www.facebook.com/externalhit_uatext.php) If you plan to scrape any links to websites you can control, please ensure that this user agent isn't blocked and returns valid opengraph data, for the best results.

Below is an example of URL enrichment as well as the resulting message structure:

name	type	description	default	optional
id	string	The message ID. This is either created by Stream or set client side when the message is added.		✓
html	string	The safe HTML generated from the raw text message. This field can only be set using server-side APIs or via the import		✓
type	string	The message type. See below for more information.		✓
user	object	The author user object. Schema is as described in the Setting the user portion of the docs.		✓
attachments	array	The list of attachments, either provided by the user or generated from a command or as a result of URL scraping. A message can have at most 30 attachments.		✓
latest_reactions	array	The latest reactions to the message created by any user. (Max 10 reactions)		✓
own_reactions	array	The array of reactions added to the message by the current user. e.g. [ReactionObject1, ReactionObject2].		✓
reaction_counts	object	The reaction count by type for this message e.g. {"haha": 3, "angry": 2}. Please use reaction_groups instead, this field only exists for compatibility reasons.		✓
reply_count	integer	Reserved field indicating the number of replies for this message.		✓
parent_id	string	The ID of the parent message, if the message is a reply.		✓
created_at	date	Reserved field indicating when the message was created.		✓
updated_at	date	Reserved field indicating when the message was updated last time.		✓
deleted_at	date	Reserved field indicating when the message was deleted.		✓
mentioned_users	array of users	The list of users that are mentioned in this message.		✓
message_text_updated_at	date	Field indicating when the message text was updated last time	-	✓
reaction_groups	object	The reaction groups by type. For example: {clap: {count: 5, sum_scores: 13, first_reaction_at: "2024-09-05T13:17:11.454912Z", last_reaction_at: "2024-09-10T21:23:12.675478Z"}}	-	✓

Chat supports different types of messages. The type of the message is set by the APIs or by chat bots and custom commands.

Name	Description
regular	A regular message created in the channel. This is the default type for messages posted on a channel.
ephemeral	A temporary message which is only delivered to one user. It is not stored in the channel history. Ephemeral messages are normally used by commands (e.g. /giphy) to prompt messages or request for actions.
error	An error message generated as a result of a failed command. It is also ephemeral, as it is not stored in the channel history and is only delivered to one user.
reply	A message in a reply thread. Messages created with parent_id are automatically of this type.
system	A message generated by a system event, like updating the channel or muting a user.
deleted	A soft deleted message.