Slack and Discord are chat apps until you check the disk: each routinely accumulates 2-15 GB of caches on a Mac that has been signed in for a year. Every thumbnail, animated emoji and scrolled-past video lands on disk and mostly never leaves.

Where it hides

App	Cache path	Notes
Slack	~/Library/Application Support/Slack/Cache + Service Worker/CacheStorage	Per-workspace data lives beside it — do not nuke the whole folder
Discord	~/Library/Application Support/discord/Cache + Code Cache	Same structure as Slack (both are Electron)

The safe delete

# quit the app first, then:
rm -rf ~/Library/Application\ Support/Slack/Cache/*
rm -rf ~/Library/Application\ Support/Slack/Service\ Worker/CacheStorage/*
rm -rf ~/Library/Application\ Support/discord/Cache/*
rm -rf ~/Library/Application\ Support/discord/Code\ Cache/*

Only ever delete the Cache and Code Cache subfolders — deleting the parent removes your login state and workspace data. Both apps rebuild caches on first launch (slower first scroll, then normal).

Make it recurring

A weekly launchd job or cron-style reminder is enough; the caches regrow but each pass reclaims 2-8 GB. Add both paths to the same script that clears your dev caches — see the package-manager guide for a combined template. Automation fans can hand this layer to MacCleaner PRO as well.

Why Electron apps are like this

Slack and Discord are Chromium apps: they inherit Chrome's aggressive cache strategy, but unlike Chrome they expose no "clear cache" button. That is why the folders grow unchecked — and why the manual routine above is the only first-party fix. The same class of problem, for build tools, is covered in Docker's disk guide; for the full disk picture see System Data explained and the ten-second estimator.