Why Can 39;t I Download Files From Slack
Sherri Herston
To help you work with your team in Slack, you can add files to your workspace. Files are searchable and shareable across Slack, making it easier for everyone to find the information they need and work together.
Slack will include a preview of a file as part of your message. If you share an image, the preview will only display inline if it's smaller than 11,000 pixels on the longest side, or less than 45 million pixels total. Microsoft Office files that are larger than 50 MB will not display a preview.
Since files can represent complex information, an app that uses files well can communicate more succinctly and precisely. In this guide, we'll explore the two ways to work with files. Here are the distinct differences.
Either way, once your upload succeeds, you'll see an HTTP response from Slack containing an "ok": true field, plus a file object. For more detail on file objects and the fields contained inside, a look at the file object documentation is highly recommended.
If, however, you wish to flex your file skills by sharing files hosted outside of Slack, providing custom unfurls, or fine-tuning the way your files appear in Slack searches: continue reading for guidance on remote files.
Note on terminology
Remote files are "added" to Slack, not "uploaded." Adding a remote file to Slack makes Slack aware of its existence. Once that's done, "sharing" a remote file, like sharing a direct upload file, brings the file into a conversation. So a remote file must be "added" before it is "shared".
Working with remote files requires a distinct set of scopes from those involved in direct upload. Again, under the Apps page of your app, choose the OAuth & Permissions sidebar to select scopes.
There is no write scope for remote files. Remote files exist across the whole workspace (or organization, for Enterprise Grid). Because of that, remote files must be added by bots with the bot scope, not by an individual user.
To subscribe to any file events, use the Event Subscriptions tab under your Apps page. One event that can be especially useful to apps that work with remote files is the link_shared event, which notifies your app when a link has been shared so that you can unfurl it. Add any App Unfurl Domains that relate to your file service under that same tab in the Apps page.
Once your upload succeeds, you'll see an HTTP response from Slack containing an "ok": true field, plus a file object. For more detail on file objects and the fields contained inside, a look at the file object documentation is highly recommended.
You'll see the external_id returned to you on the file object in the Slack response, as well as a file_id. Either of these ids can be stored and used to query the files.remote.info method to access other information about the file.
A word about tokens: the files.remote.share method may be called with either a bot or a user token. The bot token shares the file from your app, while the user token shares the file from the user associated with your user token. Use the bot token to share to channels that the bot has access to; use the user token to share to channels that the user has access to.
For use specifically with a file unfurl, you can set the hide_color field to true to remove the color bar from a message. This property works only with a file block; if this property is included along with other blocks (for example, a section block), the chat.unfurl method will throw an error.
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