# How often NotchStar updates system stats

> The System tab samples once a second, and only while it is on screen. The Monitor section in Disk samples every 3 seconds, ports about every 9.

Canonical: https://www.notchstar.com/help/how-often-notchstar-updates-system-stats/
Last updated: 2026-11-04

Published 2026-11-04.

NotchStar's System tab takes a new reading once a second, and only while that tab is on screen. When the notch is closed, or you are on another tool, nothing is sampled. There is no background process collecting history.

## The three clocks

| Where | How often | When it runs |
|---|---|---|
| System tab: CPU, memory, disk, battery, network | Once a second | Only while the System tab is open |
| Disk tab, Monitor, Usage: busiest processes | Every 3 seconds | Only while Monitor is open |
| Disk tab, Monitor, Ports: listening ports | About every 9 seconds | Only while Monitor is open |

The ports list is refreshed on every third pass of the 3 second loop, because listing ports and reading each process's folder costs more than reading counters.

## What this means in practice

- Open the tab and the first CPU reading is 0 and the network speed shows a dash. Both need two samples, so they are real after about a second.
- NotchStar keeps no history of CPU or memory. When you close the tab, the readings are gone.
- A short spike lasting less than a second can fall between two samples.

## Why it works this way

Sampling only when you can see the numbers keeps the cost near zero when you are not looking. The Disk tab goes further: a scan of caches, duplicates or large files starts only when you press its button. Read [whether the System tab affects battery](https://www.notchstar.com/help/does-notchstar-system-stats-drain-battery/) for the cost side.

The feature pages have the full lists: [System stats](https://www.notchstar.com/features/system-stats/) and [Disk](https://www.notchstar.com/features/disk/). For what the Ports table shows and when it refreshes, see [the Ports list columns](https://www.notchstar.com/help/notchstar-ports-list-columns/).

## Quick answers.

### Does NotchStar sample when the notch is closed?

No. The sampling loop belongs to the tab's view. When the notch is closed or you switch tool, the view goes away and the loop stops.

## Keep reading.

- [CPU, memory, disk, battery and network](https://www.notchstar.com/features/system-stats/): Live CPU, memory, disk, battery and network speed gauges in your Mac notch. Sampling only runs while the tab is open, so it stays light.
- [Disk space, duplicates, apps and cleanup](https://www.notchstar.com/features/disk/): See free space, find big folders, duplicates and app leftovers, compress media and clean caches from your Mac notch. Everything goes to the Trash.
- [Does NotchStar system stats drain your battery?](https://www.notchstar.com/help/does-notchstar-system-stats-drain-battery/): The System tab reads a few counters once a second and only while it is open. No battery cost has been measured, so none is claimed.
- [What the NotchStar Ports list shows](https://www.notchstar.com/help/notchstar-ports-list-columns/): Ports lists every TCP port something is listening on, with the project folder, the command, local or network, and Open, Show and Stop buttons.

## More in System stats.

- [What the CPU gauge in NotchStar shows](https://www.notchstar.com/help/cpu-usage-gauge-in-notchstar/): The CPU ring in the NotchStar System tab shows how busy your whole Mac is, as a percentage, sampled once a second while the tab is open.
- [What the memory gauge in NotchStar shows](https://www.notchstar.com/help/memory-gauge-in-notchstar/): The memory ring in NotchStar counts active, wired and compressed memory against your Mac's total RAM. Cached files are not counted.
- [What the disk gauge in NotchStar shows](https://www.notchstar.com/help/disk-gauge-in-notchstar/): The disk ring in the System tab shows how full your startup volume is, counting space macOS can reclaim as free, so it can differ from Terminal.
- [What the battery gauge in NotchStar shows](https://www.notchstar.com/help/battery-gauge-in-notchstar/): The battery ring shows charge level, turns green and reads Charging while plugged in, turns red under 20 percent. It does not show time remaining.
- [How NotchStar measures network speed](https://www.notchstar.com/help/network-speed-in-notchstar/): NotchStar shows download and upload speed in bytes per second from your WiFi and Ethernet interfaces, so VPN traffic is not counted twice.
- [Does NotchStar system stats drain your battery?](https://www.notchstar.com/help/does-notchstar-system-stats-drain-battery/): The System tab reads a few counters once a second and only while it is open. No battery cost has been measured, so none is claimed.