# How NotchStar measures network speed > NotchStar shows download and upload speed in bytes per second from your WiFi and Ethernet interfaces, so VPN traffic is not counted twice. Canonical: https://www.notchstar.com/help/network-speed-in-notchstar/ Last updated: 2026-11-04 Published 2026-11-04. NotchStar shows your current download and upload speed next to the rings in the System tab. The figures are bytes per second, measured from your WiFi and Ethernet interfaces, and they update once a second while the tab is open. ## How it is measured Your Mac keeps a running count of bytes received and sent on each network interface. NotchStar reads those counters every second and divides the difference by the time between the two reads. It only counts interfaces whose names start with `en`, which covers WiFi and Ethernet. VPN tunnels and other virtual interfaces are left out, because their traffic also passes through the real interface and would be counted twice. The counters are 32 bit and wrap around. NotchStar works out each interface's change on its own, so a wrap does not produce a huge false spike. ## Reading the units The readout switches unit as the number grows: B/s, KB/s, MB/s, then GB/s, each step being 1024. These are bytes, not bits. Internet plans are usually sold in bits, so divide the plan by eight to compare. ## Limits - A dash shows until the second sample, about one second after opening the tab. - It is a total for the Mac. It does not say which app is using the bandwidth. - It measures traffic, not the speed your connection could reach. It is not a speed test. For the other rings, see the [System stats feature page](https://www.notchstar.com/features/system-stats/) and [what the CPU gauge shows](https://www.notchstar.com/help/cpu-usage-gauge-in-notchstar/). To see how it compares with Activity Monitor's Network tab, read [NotchStar System vs Activity Monitor](https://www.notchstar.com/help/notchstar-system-stats-vs-activity-monitor/). ## Quick answers. ### Is the speed in bits or bytes? Bytes. The readout shows B/s, KB/s, MB/s or GB/s, so a connection sold as 100 megabits a second tops out near 12 MB/s. ### Why are there dashes instead of numbers? Speed is the change between two samples, so the first reading appears about a second after you open the tab. ## 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. - [How often NotchStar updates system stats](https://www.notchstar.com/help/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. - [NotchStar System tab vs Activity Monitor](https://www.notchstar.com/help/notchstar-system-stats-vs-activity-monitor/): NotchStar gives five readings at a glance. Activity Monitor gives per process detail. What each shows, and when to open which. - [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. ## 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 often NotchStar updates system stats](https://www.notchstar.com/help/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. - [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.