Why Slack and Discord Are Quietly Eating 10+ GB of Your Mac

If Slack feels heavier than an app that displays text messages has any right to be, that’s because it’s not really an app — it’s a bundled copy of Chrome running your workspace as a website, and like any browser, it caches aggressively and never cleans up after itself.

du -sh ~/Library/Application\ Support/Slack
du -sh ~/Library/Application\ Support/discord

2–8 GB per app is typical after a year of daily use across a few workspaces or servers. Teams running Slack, Discord, Notion, and a couple of other Electron apps simultaneously routinely carry 15–25 GB in this category alone, split across apps that all look small in Finder because Finder shows the .app bundle size, not the data each one has written elsewhere.

Slack specifically

Slack’s own cache breaks down into a few distinct pieces, and they’re not equally safe:

du -sh ~/Library/Application\ Support/Slack/Cache          # Chromium's HTTP cache — safe
du -sh ~/Library/Application\ Support/Slack/Service\ Worker # PWA service worker cache — safe
du -sh ~/Library/Application\ Support/Slack/Local\ Storage  # per-workspace settings — leave alone
du -sh ~/Library/Application\ Support/Slack/IndexedDB       # message search index, draft messages

Cache and Service Worker are unambiguously safe — standard browser-cache equivalents, rebuilt automatically as you use the app:

rm -rf ~/Library/Application\ Support/Slack/Cache
rm -rf ~/Library/Application\ Support/Slack/Service\ Worker

IndexedDB is worth being more careful with — it holds Slack’s local search index and, in some versions, unsent draft messages. Quit Slack fully before touching it, and know that clearing it means Slack rebuilds its local search index from the server on next launch, which can take a few minutes for workspaces with a long history.

Discord specifically

Discord’s cache lives in a near-identical layout, being built on the same Electron/Chromium base:

du -sh ~/Library/Application\ Support/discord/Cache
du -sh ~/Library/Application\ Support/discord/Code\ Cache
du -sh ~/Library/Application\ Support/discord/GPUCache

All three are standard Chromium sub-caches — safe to delete, and Discord has a Settings → Advanced → Clear Cache button that does the same thing without leaving the app.

The pattern generalizes to every Electron app

Notion, Figma’s desktop client, Obsidian (with community plugins that embed browser views), Postman, and dozens of other tools you probably have installed are Electron apps with the identical Cache / Code Cache / GPUCache structure sitting under their own folder in ~/Library/Application Support/<AppName>:

# Find every Electron-style Cache folder across your installed apps
find ~/Library/Application\ Support -maxdepth 2 -type d -name "Cache" -exec du -sh {} \; 2>/dev/null | sort -hr

The Cache, Code Cache, and GPUCache subfolder names are consistent across almost every Electron app precisely because they all embed the same Chromium engine — once you recognize the pattern in one app, you can find it in all of them.

What’s not safe to touch

Local Storage and any folder literally named Preferences, Settings, or containing a config.json holds your actual app configuration — logged-in accounts, workspace lists, keybindings. These sit alongside the cache folders but are a small fraction of the size and are exactly what you’d lose by deleting the app’s entire Application Support folder instead of just the Cache subdirectories inside it. Stick to deleting folders literally named Cache, Code Cache, or GPUCache and you won’t touch anything that matters.

The commands above are free and they work. DevCruft, a free Mac app for developers that’s in development, is being designed to find every Electron app’s cache on your disk and rank them by size, without you needing to know which of the dozen apps you’ve installed are secretly running Chromium underneath. You can join the waitlist to hear when it launches.

For the disk-hungry apps developers install specifically for their work, see the VS Code and JetBrains cache guide.