The short answer
Yes. Rebuilt or re-downloaded automatically when needed.
What is it?
Data the Slack app stores through a service worker so it starts quickly and copes with brief offline moments: app code and cached workspace resources. It can grow to hundreds of MB or more.
What happens if you delete it?
Rebuilt on the next launch; Slack may start more slowly and needs a connection the first time.
How to remove it properly
Quit Slack, then move ~/Library/Application Support/Slack/Service Worker/CacheStorage to the Trash.
Quit the app that uses it, then move it to the Trash. Empty the Trash when you’re sure.
How MoreRoom helps
MoreRoom recognises this item, shows its real size and when it was last used, and labels it “Safe to remove”. In the free version you can move it to the Trash in one click, with Undo; Pro collects every safe item at once.
Frequently asked questions
Is it safe to delete Slack’s Service Worker cache on Mac?
Yes. Rebuilt or re-downloaded automatically when needed. Rebuilt on the next launch; Slack may start more slowly and needs a connection the first time.
Will Slack offline cache come back after I delete it?
Yes. Rebuilt on the next launch; Slack may start more slowly and needs a connection the first time.
How do I remove Slack offline cache properly?
Quit Slack, then move ~/Library/Application Support/Slack/Service Worker/CacheStorage to the Trash.