---
id: comparisons.activity-monitor-vs-where-did-my-space-go
url: https://storagestudio.us/faq/comparisons/activity-monitor-vs-where-did-my-space-go
category: "Comparisons & alternatives"
subcategory: "macOS's own storage tools"
question: "Can't Activity Monitor show me what's filling my disk?"
alt_questions:
  - "activity monitor disk tab vs storage studio"
  - "which process is writing to my disk mac"
  - "activity monitor bytes written storage"
  - "find app filling up disk mac"
  - "disk usage per app mac"
short_answer: "Activity Monitor shows which processes are reading and writing now. Storage Studio's 'Where did my space go?' shows how free space changed over a period, what grew, and which app was responsible when it can tell."
tags: ["activity monitor", "space history", "apps"]
related: ["https://storagestudio.us/faq/comparisons/can-a-disk-analyser-tell-me-where-my-space-went", "https://storagestudio.us/faq/comparisons/low-space-warnings-vs-macos-disk-almost-full-alert"]
applies_to: "all"
last_reviewed: 2026-10-01
---

# Can't Activity Monitor show me what's filling my disk?

Partly. Activity Monitor's **Disk** tab shows how much each running process is reading and writing **right now** and since it started — useful for spotting a busy app, but it doesn't tell you how much space was used up, where it went, or what happened while you weren't looking.

Storage Studio answers the space question directly:

- it watches free space over time and can break down any period you pick — what grew, what was freed, and what it couldn't account for;
- it names the app responsible when it can identify one;
- it measures temporary and cache areas and attributes what's there to the app that put it there.

Use Activity Monitor to see who's busy now, and **Where did my space go?** (More •••) to see where the room went. See [What's Using Space](https://storagestudio.us/manual/whats-using-space).