---
id: mac-storage-basics.how-do-i-see-which-app-is-writing-to-my-disk
url: https://storagestudio.us/faq/mac-storage-basics/how-do-i-see-which-app-is-writing-to-my-disk
category: "Mac storage basics"
subcategory: "Memory, swap and speed"
question: "How do I see which app is writing the most to my disk?"
alt_questions:
  - "activity monitor disk tab"
  - "bytes written per app"
  - "disk activity mac"
  - "app using disk heavily"
short_answer: "Open Activity Monitor's Disk tab and sort by Bytes Written. Backup, sync and indexing processes write a lot after big changes; constant writing by an ordinary app is worth checking."
tags: ["activity monitor", "disk activity", "performance"]
related: ["https://storagestudio.us/faq/mac-storage-basics/why-does-my-mac-fill-up-on-its-own", "https://storagestudio.us/faq/mac-storage-basics/does-spotlight-indexing-use-disk-space"]
applies_to: "all"
last_reviewed: 2026-10-01
---

# How do I see which app is writing the most to my disk?

Open **Activity Monitor**, click the **Disk** tab and sort by **Bytes Written**. The top entries are writing the most since they started. A graph at the bottom shows overall reads and writes.

Heavy writing from backup, sync, indexing and photo-analysis processes is normal for a while after big changes. An ordinary app writing continuously may be filling caches or logs — check its settings or update it.