Slack – How to Invite Multiple Users to a Channel

On the browser view, click on the drop down menu next to your team's name on Preferences. Then click on Messages and media on the left-hand side. Then, under the section Inline Media & Links you will find checkboxes for

• Expand images and files uploaded to Slack
• Expand links to images, video and audio from external sources
  • Even if it is an image larger than 2MB
• Expand website links to show a preview of the content, when available

Uncheck whichever of those that you want and you are set!

In order to store and print messages from a channel you use the export feature in the client or develop a script that uses the web API.

The export feature works fine, however there are a few constrains:

• can only be done by admins or owners
• only works for public channels
• the format is JSON (one file per channel, each message is one element in a JSON array)

See here for further information on the Slack help pages.

I also found a Slack App called Export that allows to export the full content of a channel for storage and later printing. This app supports exporting for any channel the user as access to including private channels. Messages can e.g. be exported in HTML for printing with the browser. The app works fine, but the output quality is a bit rough and seams to lack images and conversation of Slack link syntax to HTML.

Another approach is to develop your own script. You only need to read all messages of a channel directly via web API (with conversations.history]3) and then process it further (e.g. convert to output file for printing). That will work for both public and private channels, but obviously requires a bit of coding.