Unfurling links will change slightly on August 18, 2021

On September 1, 2021, the link_shared event is changing. The change will happen for free teams on September 1, and will roll out to paid teams over the following weeks.

The chat.unfurl method will also accept new arguments.

Changes to link_shared will help enable a smoother unfurl experience for apps that haven't yet been installed.

What's changing

The link_shared event will now be sent when a user types a link into the message composer, in addition to when the message is sent to a channel.

As part of this change, two new fields will be included:

  • unfurl_id, which identifies the link and can be used to supply the chat.unfurl method.
  • source, an enumerated string that tells you whether the event happened in composer ("source": "composer") or in a sent message ("source": "conversations_history).

A full payload for the link_shared event sent when a link is typed into the message composer is:

    "type": "link_shared",
    "channel": "COMPOSER",
    "is_bot_user_member": true,
    "user": "Uxxxxxxx",
    "message_ts": "Uxxxxxxx-909b5454-75f8-4ac4-b325-1b40e230bbd8-gryl3kb80b3wm49ihzoo35fyqoq08n2y",
    "unfurl_id": "Uxxxxxxx-909b5454-75f8-4ac4-b325-1b40e230bbd8-gryl3kb80b3wm49ihzoo35fyqoq08n2y",
    "source": "composer",
    "links": [
            "domain": "example.com",
            "url": "https://example.com/12345"
            "domain": "example.com",
            "url": "https://example.com/67890"
            "domain": "another-example.com",
            "url": "https://yet.another-example.com/v/abcde"

Note that channel in these messages represents the fact that this event comes from the message composer, not any particular channel for the message. If you make assumptions about the channel for link_shared events being a real channel, those assumptions won't work for the COMPOSER channel.

Similarly, the message_ts for these events will not be a valid timestamp for any method besides chat.unfurl.

As mentioned, chat.unfurl will continue to accept the combination of channel and ts you find in these link_shared events, even though they're not strictly channels or timestamps. But you can also use the unfurl_id and source parameters (if you use one, you must use both together) to call chat.unfurl.

How to respond or prepare

If you don't want to make use of new unfurl experiences, you can filter out link_shared events from the source of composer.

If you do wish to use new unfurls, check the source and make sure your logic doesn't assume that channel and message_ts are valid channels and timestamps.

What happens if I do nothing?

Your app could receive invalid channel errors if it tries to use Slack APIs in response to receiving a link_shared event.

When is this happening

This change happens on September 1, 2021 for free teams, with a gradual rollout to paid teams over the next month. As always, feedback is welcome at feedback@slack.com.