How to clear the Slack cache on your Mac (yes, it's safe to delete)

Yes, it's safe to deleteDiskmack safety tier: Safe to clean

~/Library/Application Support/Slack/Cache~/Library/Application Support/Slack/Service Worker

Yes, it's safe to clear the Slack cache. The two folders that matter, Cache and Service Worker inside ~/Library/Application Support/Slack, hold nothing but re-downloadable content: cached images, file previews, and the app's offline web assets. Quit Slack, move both folders to the Trash, and Slack rebuilds the Service Worker data on its next launch and re-downloads images as you use it. Your messages, files, and sign-ins are untouched.

What it is

The Slack desktop app is built on Electron, which means it is essentially a Chromium browser dedicated to one website. Like any browser, it keeps a cache. The Cache folder stores the images, avatars, GIFs, file previews, and other web content Slack has already downloaded, so channels render instantly instead of re-fetching every profile photo and inline screenshot from the network. The Service Worker folder is Slack's offline web app cache: the scripts and assets the app stores locally so it can start quickly and keep behaving when your connection hiccups.

Both folders grow with use. Every image posted in every channel you open gets cached, and people who sit in several busy workspaces all day accumulate cached media fast. Slack does some housekeeping of its own, but not aggressively, so on a Mac that lives in Slack the Cache folder commonly reaches hundreds of megabytes and can climb past a gigabyte or two over months. The Service Worker folder is usually smaller, but it is part of the same disposable pile, which is why the two are worth clearing together.

Is it safe to delete?

Yes. Neither folder contains anything original. Your messages, shared files, drafts, and workspace settings live on Slack's servers, and files you explicitly saved went to your Downloads folder (or wherever you chose), not into this cache. Per Slack's own behavior, the Cache contents are re-downloaded as you use Slack, and the Service Worker data is rebuilt on the next launch. Deleting them cannot cost you data.

The only price is a brief warm-up. The first time you scroll a channel after clearing, Slack fetches its images and previews from the network again, so things load a beat slower for a little while. That is the whole downside. In exchange, clearing the cache is also the standard fix when Slack shows stale images or misbehaves after an update. Diskmack identifies both of these folders automatically and cleans them the safe way.

How to check its size

In Finder: In Finder, choose Go > Go to Folder (or press Command-Shift-G), type ~/Library/Application Support/Slack and press Return. Click the Cache folder once and press Command-I to see its size, then do the same for the Service Worker folder. If Finder says the folder can't be found, you have the Mac App Store version of Slack: its copy lives at ~/Library/Containers/com.tinyspeck.slackmacgap/Data/Library/Application Support/Slack, with the same two folders inside.

In Terminal:

du -sh ~/Library/"Application Support/Slack/Cache" ~/Library/"Application Support/Slack/Service Worker"

How to clean it

Quit Slack completely: click the Slack window, press Command-Q, and make sure it is gone from the Dock (right-click its Dock icon and choose Quit if it is still running).
In Finder, choose Go > Go to Folder (Command-Shift-G), type ~/Library/Application Support/Slack and press Return.
Select the Cache folder and press Command-Delete to move it to the Trash.
Select the Service Worker folder and press Command-Delete as well.
Leave the other folders in there alone; they hold your sign-ins and local settings.
Reopen Slack. It rebuilds the Service Worker data on launch and re-downloads images as you browse.
Empty the Trash to actually reclaim the space.

Slack must not be running while you delete these folders. An open Slack holds them in use, and clearing a live cache can leave the app confused until you restart it anyway. Mac App Store installs keep the same two folders under ~/Library/Containers/com.tinyspeck.slackmacgap/Data/Library/Application Support/Slack; the steps are otherwise identical.

Will it come back?

Yes, and quickly, because that is the folder doing its job. The Service Worker cache is rebuilt the moment Slack launches again, and the Cache folder refills as you open channels and Slack re-downloads the images and previews you scroll past. How fast it regrows tracks how you use Slack: a light single-workspace user might stay under a few hundred megabytes for months, while someone in several image-heavy workspaces can be back near the old size within weeks. Treat clearing it as periodic maintenance, or as the fix for a misbehaving Slack, not as a one-time cure.

Common questions

Will clearing the cache sign me out of Slack?

No. Your sign-ins and workspace list are stored in other parts of the Slack folder, not in Cache or Service Worker. After clearing, Slack opens to the same workspaces and channels, and your message history and drafts come straight back from Slack's servers.

Slack shows old images or acts glitchy. Will this fix it?

Often, yes. A stale cache is the usual culprit behind outdated avatars, broken previews, and weirdness after an update. Slack even ships a menu item for exactly this: Help > Troubleshooting > Clear Cache and Restart, which clears the same data and relaunches the app for you.

Can I just delete the whole ~/Library/Application Support/Slack folder?

You can, but it is a full reset: you get signed out of every workspace and lose local preferences, so you will redo setup on next launch. Unless you are deliberately wiping the app, stick to the Cache and Service Worker folders.

How big does the Slack cache actually get?

It depends entirely on usage. A light user might find a hundred megabytes or so, while heavy multi-workspace users can accumulate a gigabyte or more over months. The du command above gives you the real number for your Mac before you decide it is worth clearing.