---
title: "Memory footprint (phys_footprint) · MacMelon"
description: "A process's memory footprint is the memory macOS charges to it, including compressed memory. Sentinely uses it instead of resident size (RSS)."
url: "https://macmelon.com/glossary/memory-footprint"
---

# Memory footprint

The memory macOS charges to a process, including memory it has compressed. Sentinely's unit for estimates and receipts.

macOS keeps several numbers for each process. Resident size, often called RSS, counts pages currently in RAM. It leaves out compressed memory and counts shared pages in every process that uses them. The memory footprint, phys\_footprint in the kernel, is the memory macOS itself charges to the process, including what has been compressed.

[Sentinely](https://macmelon.com/apps/sentinely) estimates with the footprint and never with RSS. For apps made of many processes, such as Electron chat apps, processes share some memory, so adding their footprints can overstate what a fix will give back. Those estimates are shown as "up to", and the [measured receipt](https://macmelon.com/glossary/measured-receipt) reports what actually came back.

## Apps

[No more Force Quit in the middle of a build. ### Sentinely](https://macmelon.com/apps/sentinely)

## Related guides

[### How to find what's slowing down your Mac](https://macmelon.com/guides/how-to-find-what-is-slowing-down-your-mac)

## Related use cases

[### Find out why your Mac is slow](https://macmelon.com/use-cases/find-out-why-your-mac-is-slow)[### When Slack, Teams, or Discord slows your Mac](https://macmelon.com/use-cases/slack-teams-and-discord-slowing-your-mac)[### When VS Code or Cursor slows your Mac](https://macmelon.com/use-cases/vs-code-or-cursor-slowing-your-mac)

## Related terms

[Memory macOS has squeezed in place to make room, before it writes anything to disk. ### Compressed memory](https://macmelon.com/glossary/compressed-memory)[Sentinely's record of a fix: what was freed and what changed for you, measured after the fix rather than promised before it. ### Measured receipt](https://macmelon.com/glossary/measured-receipt)[How hard macOS is working to make room in memory. The signal that a Mac is actually short on memory, not just using it. ### Memory pressure](https://macmelon.com/glossary/memory-pressure)