Provide custom unfurl behavior for user-posted URLs

Facts

Method access

HTTP
JavaScript
Python
Java
HTTP
POSThttps://slack.com/api/chat.unfurl
Bolt for Java
app.client().chatUnfurl
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Bolt for Python
app.client.chat_unfurl
Powered by Bolt

Content types

application/x-www-form-urlencodedapplication/json
  • Rate limits

    Tier 3
  • Arguments

    ArgumentTypeDescription
    tokenRequired

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

    Examplexxxx-xxxxxxxxx-xxxx
    channelRequired
    string

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

    ExampleC1234567890
    tsRequired
    string

    Timestamp of the message to add unfurl behavior to.

    unfurlsRequired
    string

    URL-encoded JSON map with keys set to URLs featured in the the message, pointing to their unfurl blocks or message attachments.

    source
    string

    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.

    Examplecomposer
    unfurl_id
    string

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

    ExampleUxxxxxxx-909b5454-75f8-4ac4-b325-1b40e230bbd8
    user_auth_blocks

    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

    user_auth_message

    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_required
    boolean

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

    Default: 0

    Exampletrue
    user_auth_url

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

    Examplehttps://example.com/onboarding?user_id=xxx

    This method supports application/json via HTTP POST. Present your token in your request's Authorization header. Learn more.

    Example responses

    Common successful response

    Typical, minimal success response

    {
        "ok": true
    }
    Common error response

    Typical error response

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

    This method unfurls a linkβ€”either in the message composer or in a posted message.

    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. unfurl_id and source are the preferred choice.

    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 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, and if the preview is not provided, 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.

    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.

    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 params in the response.

    ErrorDescription
    missing_channel

    The request is missing the channel parameter

    missing_ts

    The request is missing the ts parameter

    cannot_find_channel

    The specified channel could not be located for this token.

    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.

    missing_unfurls

    The request is missing the unfurls parameter.

    invalid_unfurls_format

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

    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.

    cannot_prompt

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

    cannot_find_message

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

    cannot_unfurl_message

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

    cannot_auth_user

    The current user cannot be authenticated.

    not_authed

    No authentication token provided.

    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.

    account_inactive

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

    token_revoked

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

    token_expired

    Authentication token has expired

    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.

    org_login_required

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

    ekm_access_denied

    Administrators have suspended the ability to post a message.

    missing_scope

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

    not_allowed_token_type

    The token type used in this request is not allowed.

    method_deprecated

    The method has been deprecated.

    deprecated_endpoint

    The endpoint has been deprecated.

    two_factor_setup_required

    Two factor setup is required.

    enterprise_is_restricted

    The method cannot be called from an Enterprise.

    is_bot

    This method cannot be called by a bot user.

    team_access_not_granted

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

    invalid_arguments

    The method was either called with invalid arguments or some detail about the arguments passed are invalid, which is more likely when using complex arguments like blocks or attachments.

    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_array_arg

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

    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_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.

    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.

    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.

    ratelimited

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

    accesslimited

    Access to this method is limited on the current network

    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

    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.

    Warnings

    This table lists the expected warnings that this method will return. However, other warnings can be returned in the case where the service is experiencing unexpected trouble.

    WarningDescription
    missing_charset

    The method was called via a POST request, and recommended practice for the specified Content-Type is to include a charset parameter. However, no charset was present. Specifically, non-form-data content types (e.g. text/plain) are the ones for which charset is recommended.

    superfluous_charset

    The method was called via a POST request, and the specified Content-Type is not defined to understand the charset parameter. However, charset was in fact present. Specifically, form-data content types (e.g. multipart/form-data) are the ones for which charset is superfluous.

    Arguments

    Need a token? Create and install a Slack app to begin.
    This will make a real API request. Beware of using it with live workspaces.

    API response


    Submit your arguments to see the API response

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