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chat.unfurl method

Facts​

DescriptionProvide custom unfurl behavior for user-posted URLs
Method Access
POST https://slack.com/api/chat.unfurl
Scopes
Bot token:
User token:
Content types
application/x-www-form-urlencoded
application/json
Rate LimitsTier 3: 50+ per minute

Arguments​

Required arguments

tokenstringRequired

Authentication token bearing required scopes. Tokens should be passed as an HTTP Authorization header or alternatively, as a POST parameter.

Example: xxxx-xxxxxxxxx-xxxx

Optional arguments

channelstringOptional

Channel ID of the message. Both channel and ts must be provided together, or unfurl_id and source must be provided together.

tsstringOptional

Timestamp of the message to add unfurl behavior to.

unfurlsstringOptional

URL-encoded JSON map with keys set to URLs featured in the the message, pointing to their unfurl blocks or message attachments. Either unfurls or metadata must be provided.

user_auth_messageOptional

Provide a simply-formatted string to send as an ephemeral message to the user as invitation to authenticate further and enable full unfurling behavior. Provides two buttons, Not now or Never ask me again.

user_auth_requiredbooleanOptional

Set to true or 1 to indicate the user must install your Slack app to trigger unfurls for this domain

Default: 0
user_auth_urlOptional

Send users to this custom URL where they will complete authentication in your app to fully trigger unfurling. Value should be properly URL-encoded.

Example: https://example.com/onboarding?user_id=xxx
user_auth_blocksOptional

Provide a JSON based array of structured blocks presented as URL-encoded string to send as an ephemeral message to the user as invitation to authenticate further and enable full unfurling behavior

unfurl_idstringOptional

The ID of the link to unfurl. Both unfurl_id and source must be provided together, or channel and ts must be provided together.

Example: Uxxxxxxx-909b5454-75f8-4ac4-b325-1b40e230bbd8
sourcestringOptional

The source of the link to unfurl. The source may either be composer, when the link is inside the message composer, or conversations_history, when the link has been posted to a conversation.

Example: composer
metadataOptional

JSON object with an entities field providing an array of Work Object entities. Either unfurls or metadata must be provided.

Usage info​

This method unfurls a link—either in the message composer or in a posted message.

Ensure that the links:write scope is added to your app settings for apps that will be performing app unfurling.

This method supports both granular bot and user tokens. The bot token is recommended.

Both unfurl_id and source must be provided together, or channel and ts must be provided together.

The first time this method is executed with a particular ts and channel (or unfurl_id and source) combination, the valid unfurls attachments you provide will be attached to the message. Subsequent attempts with the same ts and channel values will modify the same attachments, rather than adding more.

The ts value you supply must correspond to a message in the specified channel. Also, the message must contain a fully-qualified URL pointing to a domain that is already registered and associated with your Slack app.

The user_auth_required parameter is optional. By providing a 1 or true value, it will require the user posting the link first authenticate themselves with your app. See also the authenticated unfurling docs.

If you'd rather directly point users to a specific page on your server to authenticate, pass a valid URL using the user_auth_url parameter. When sending this parameter via application/x-www-form-urlencoded GETs or POSTs, values must be URL-encoded such that https://example.com/onboarding?user_id=xxx becomes https%3A%2F%2Fexample.com%2Fonboarding%3Fuser_id%3Dxxx.

Or, you can send an ephemeral message to that user by providing a simple string-based user_auth_message value or JSON array of blocks using user_auth_blocks. Simple slack message formatting like *bold*, _italics_, and linking is supported, so you can wrap your custom URLs in a blanket of situationally accurate, actionable text.

user_auth_message offers two default buttons, Not now and Never ask me again which allows your app to prompt a user multiple times before opting out of an install. To make your ephemeral message extra fancy, you can also use user_auth_blocks which will override the default buttons. Using both properties shows the user_auth_message in a notification and the user_auth_blocks in the ephemeral message.

Specifying user_auth_url or user_auth_message will automatically imply user_auth_required being set to true. If both user_auth_url and user_auth_message are provided, user_auth_message takes precedence.

The unfurls parameter​

The unfurls parameter expects a URL-encoded string of JSON. Unlike chat.postMessage's attachments parameter, it does not expect a JSON array but instead, a hash keyed on the specific URLs you're offering an unfurl for. Each URL can have a single attachment, including message buttons.

You can define your own preview for a link that you're unfurling inside the message composer by passing the preview field:

"unfurls": {
  "https://example.com": {
    "blocks": [...],
    "preview": {
        "title": {
          "type": "plain_text",
          "text": "custom preview"
        },
        "icon_url":
          "https://images.pexels.com/photos/774731/pexels-photo-774731.jpeg?auto=compress&cs=tinysrgb&dpr=1&w=500"
      }
    }
}

This preview field is optional, however, if preview and title are not provided, Canvas app unfurls will be unable to render title text. In the absence of preview for uses outside of Canvas, we will generate the preview based on the blocks layout or legacy attachment. If the preview is provided in an unfurl for a posted message, rather than a link inside the message composer, we will simply ignore this property.

Read the unfurling docs for more guidance on this parameter.

For use specifically with a file unfurl, you can set the hide_color field to true to remove the color bar from a message as in the following example:

"unfurls": {
  "https://example.com": {
    "hide_color": true,
    "blocks": [{
      "type": "file",
      "external_id": "ABCD1",
      "source": "remote",
    }]
  }
}

This property works only with a file block; if this property is included along with other blocks (for example, a section block), this method will throw an error.

The metadata parameter​

The metadata parameter expects a JSON object with entity_type and entity_payload fields, presented as a URL-encoded string. Either unfurls or metadata must be provided. Slack uses this parameter to generate a Work Object representing the resource your app is unfurling. The JSON schema of the parameter is found below:

"metadata": {
  "entities": [
    {
      "app_unfurl_url": "https://example.com/document/123?eid=123456&edit=abcxyz", 
      // URL posted by the user in a conversation
      "url": "https://example.com/document/123", 
      // URL representing the resource in the third party system
      "external_ref": {
        "id": "123", // a string ID that uniquely identifies the resource being unfurled
        "type": "document" // An optional internal type for entity in the source system. 
        // Only needed if the ID is not globally unique or needed when retrieving the item.
      },
      "entity_type": "slack#/entities/file", // entity type
      "entity_payload": {}, // entity schema
    }
  ]
}

Refer to Work Objects for more details.

Response​

Typical, minimal success response

{
  "ok": true
}

Typical error response

{
  "ok": false,
  "error": "cannot_unfurl_url"
}

As you can see, we provide a minimal positive response when your unfurl attempt is successful. When it is not, you'll receive one of the errors below and ok will be false.

Errors​

This table lists the expected errors that this method could return. However, other errors can be returned in the case where the service is down or other unexpected factors affect processing. Callers should always check the value of the ok parameter in the response.

Error
Description
access_denied

Access to a resource specified in the request is denied.

accesslimited

Access to this method is limited on the current network

account_inactive

Authentication token is for a deleted user or workspace when using a bot token.

cannot_auth_user

The current user cannot be authenticated.

cannot_find_channel

The specified channel could not be located for this token.

cannot_find_message

The ts value in the request does not match a message.

cannot_find_service

A record of your app being allowed to unfurl for this workspace could not be found.

cannot_parse_attachment

The provided unfurls argument could not be parsed or understood.

cannot_prompt

The current user has already interacted with and dismissed a prompt for this application.

cannot_unfurl_message

The URL cannot be unfurled because the URL provided does not appear in the message.

cannot_unfurl_url

The URL cannot be unfurled. This error may be returned if you haven't acknowledged a link_shared event tied to the same URL. It is also returned when the domain appears in a workspace's administrative blocklists.

deprecated_endpoint

The endpoint has been deprecated.

ekm_access_denied

Administrators have suspended the ability to post a message.

enterprise_is_restricted

The method cannot be called from an Enterprise.

error_processing_metadata

The metadata parameter was invalid.

fatal_error

The server could not complete your operation(s) without encountering a catastrophic error. It's possible some aspect of the operation succeeded before the error was raised.

internal_error

The server could not complete your operation(s) without encountering an error, likely due to a transient issue on our end. It's possible some aspect of the operation succeeded before the error was raised.

invalid_arg_name

The method was passed an argument whose name falls outside the bounds of accepted or expected values. This includes very long names and names with non-alphanumeric characters other than _. If you get this error, it is typically an indication that you have made a very malformed API call.

invalid_arguments

The method was called with invalid arguments.

invalid_array_arg

The method was passed an array as an argument. Please only input valid strings.

invalid_auth

Some aspect of authentication cannot be validated. Either the provided token is invalid or the request originates from an IP address disallowed from making the request.

invalid_charset

The method was called via a POST request, but the charset specified in the Content-Type header was invalid. Valid charset names are: utf-8 iso-8859-1.

invalid_form_data

The method was called via a POST request with Content-Type application/x-www-form-urlencoded or multipart/form-data, but the form data was either missing or syntactically invalid.

invalid_metadata_format

The metadata parameter cannot be JSON-decoded into the expected format.

invalid_post_type

The method was called via a POST request, but the specified Content-Type was invalid. Valid types are: application/json application/x-www-form-urlencoded multipart/form-data text/plain.

invalid_source

The unfurl source is invalid.

invalid_unfurl_id

The unfurl ID is invalid.

invalid_unfurls_format

The unfurls parameter cannot be JSON-decoded into a map of URLs to attachments.

method_deprecated

The method has been deprecated.

missing_channel

The request is missing the channel parameter

missing_post_type

The method was called via a POST request and included a data payload, but the request did not include a Content-Type header.

missing_scope

The token used is not granted the specific scope permissions required to complete this request.

missing_source

The request is missing the source parameter.

missing_ts

The request is missing the ts parameter

missing_unfurl_id

The request is missing the unfurl_id parameter.

missing_unfurls

The request is missing the unfurls parameter.

no_permission

The workspace token used in this request does not have the permissions necessary to complete the request. Make sure your app is a member of the conversation it's attempting to post a message to.

not_allowed_token_type

The token type used in this request is not allowed.

not_authed

No authentication token provided.

org_login_required

The workspace is undergoing an enterprise migration and will not be available until migration is complete.

ratelimited

The request has been ratelimited. Refer to the Retry-After header for when to retry the request.

request_timeout

The method was called via a POST request, but the POST data was either missing or truncated.

service_unavailable

The service is temporarily unavailable

team_access_not_granted

The token used is not granted the specific workspace access required to complete this request.

team_added_to_org

The workspace associated with your request is currently undergoing migration to an Enterprise Organization. Web API and other platform operations will be intermittently unavailable until the transition is complete.

token_expired

Authentication token has expired

token_revoked

Authentication token is for a deleted user or workspace or the app has been removed when using a user token.

two_factor_setup_required

Two factor setup is required.