SlackRevert by James Healy

- Install.
- Browse to your Slack workspace.
- Hit refresh.
- Old UX!

If you're on Chrome, or don't trust some random Extension - run this in your console instead:

localStorage.setItem("localConfig_v2", localStorage.getItem("localConfig_v2").replace(/\"is_unified_user_client_enabled\":true/g, '\"is_unified_user_client_enabled\":false'))

If you're on Mac/native client, you can enable Developer Tools and do this too (thanks to /u/guitwo on the /r/Slack Reddit):

1. Close the Slack app
2. Open the terminal and run these two commands separately:
export SLACK_DEVELOPER_MENU=true
open /Applications/Slack.app
3. Slack will open with the new theme but now we have access to its console
4. Open Slack's console by pressing command + option + I
5. Run this in Slack’s console:
localStorage.setItem("localConfig_v2", localStorage.getItem("localConfig_v2").replace(/\"is_unified_user_client_enabled\":true/g, '\"is_unified_user_client_enabled\":false'))
6. Restart Slack with command + R

You can also reverse these commands to enable the Slack Unified UX if you haven't enabled it already.

This will enable it:
localStorage.setItem("localConfig_v2", localStorage.getItem("localConfig_v2").replace(/\"is_unified_user_client_enabled\":false/g, '\"is_unified_user_client_enabled\":true'))