Emoji are everywhere now. In many applications - such as Slack - you can not type a simple emoticon based on text such as “:)” or “: D” without automatically translating it into a tiny emoji image. Fortunately, Slack lets you turn this feature off on your desktop or web client. See how you can make the necessary adjustments.
First, you need to open "Slack Preferences". At this time, you do not seem to be able to disable this feature in Slack Mobile, so we will only talk about the changes you need to make from your desktop or desktop. web client of Slack. In the desktop application of Windows, do click on the button in the upper left corner and select File> Preferences. Or you can press Ctrl + Comma.
In the Slack application for Poppy or if you are using the application on web browser, click on the workspace name in the upper left corner and select "Preferences". You can also press Command + Comma on the Mac to open "Preferences".
In the "Preferences" menu, select "Messages & media" from the sidebar.
In the "Messages and media" preferences, scroll down to the "Emoji" section and uncheck frame next to "Convert my typed emoticons into emoji".
The old school won!
Source of information: howtogeek.com