Glossary
Signal-to-noise ratio
How far a Wi-Fi signal stands above the background noise, in decibels. Higher is better.
What it is
Wi-Fi signal strength (RSSI) and noise are both measured in dBm, negative numbers where closer to zero is stronger. The difference between them is the signal-to-noise ratio (SNR).
A strong signal in a noisy place can still perform badly. SNR, not signal alone, predicts the link rate you'll get.
Why it matters
When Wi-Fi is slow, a low SNR points to interference or distance rather than your internet connection.
In Activity Monitor
Not shown. Hold Option and click the Wi-Fi menu to see RSSI, noise and channel.
In iKnowMyMac
Wi-Fi quality shows signal, noise, SNR, channel, band and link rate next to the network figures.
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