slow internet speed on mac book air

"Slow" Internet performance could indicate that the DNS settings for your notebook's wireless are either incorrect or not using the most efficient DNS servers available to it.

By default, your ISP provides you with their DNS servers. You can elect to use other ones instead to see if there is any improvement in web page "loading" times.

I suggest starting by providing us the following values from the wireless connection. To do so, hold down the option key, and then, select the Wi-Fi icon in the upper right-hand side of the macOS menu bar.

What are the values for:

• Security
• Channel
• RSSI
• Noise
• Tx Rate
• PHY Mode
• MCS Index
• NSS

Ok, thanks for providing those Wi-Fi values.

Let's take a quick look at what some of those mean, as far as, the wireless connection quality is concerned.

SNR

One quality measure is the Signal-to-Noise Ratio or SNR. SNR = RSSI - Noise. The higher the value, the better. So, in this case, SNR = 47 -(-87) = 40 dB. This would be considered an "excellent" ratio ... so, that doesn't appear to be an issue here.

MCS Index

MCS Index is a measure of the actual wireless connection's potential data rate (Tx Rate). It is comprised of a number of factors, and again, the higher the value the better. For an 802.11ac connection, 9 would be the highest value possible for 2 spatial streams (NSS = 2) with 80 MHz-wide channels. You would expect the maximum for this combination would be: 866.7 Mbps ... so this reading is a bit low of that. Nothing unusual here either.

The fact that this issue is intermittent typically indicates that Wi-Fi interference may be the culprit and not anything amiss with your Mac. I suggest when you appear to have another Internet issue to take those reading again to see if the connection has degraded. If it did not, then it's not the connection, but could be the Internet instead.

Also, be aware that the 5 GHz band's wireless signal has more difficulty traversing through objects. That's why, in order to get the best performance, a wireless device should be in the same room as the wireless router/access point for this band. The 2.4 GHz band is much less susceptible to this issue, but provides less overall bandwidth ... a tradeoff.