Why Slack uses so much on a Mac
- It's built on web technology. Each workspace runs a lot like a browser tab, so you'll see several Slack helper processes in Activity Monitor.
- Many workspaces signed in at once, each keeping its own data fresh.
- Busy channels with lots of images, animated GIFs, animated emoji and link previews.
- Huddles and screen sharing, which encode and decode video in real time.
- A large cache that has built up over months.
How to make Slack lighter
- Sign out of workspaces you don't need on this Mac. Each one costs memory even when you're not looking at it.
- Turn off animations. In Slack's Preferences, look under Accessibility for the option to allow animated images and emoji, and switch it off.
- Clear the cache. From Slack's menu bar, choose Help › Troubleshooting › Clear Cache and Restart. You stay signed in.
- Leave or mute very busy channels you only skim, so fewer messages and previews load.
- Keep Slack updated, and quit it fully (Slack › Quit Slack) instead of closing the window when you're done for the day.
Is the web version lighter?
Sometimes. Slack in a browser tab shares the browser's processes, which can use less memory than the desktop app, but you lose some desktop features. If the app is heavy on your Mac, try a day in the browser and compare in Activity Monitor.