How to match FreeBSD’s YouTube loading speed on macOS
November 25, 2025
I watch a lot of YouTube videos, and I noticed something interesting. On FreeBSD, when I skip to any part of a video, it starts playing instantly. On macOS, however, it takes a couple of seconds to load.
I wanted to fix that delay, so with help from an LLM, I changed some network settings on macOS to match FreeBSD’s behavior — and it worked perfectly! YouTube now loads just as fast as on FreeBSD.
First I feed LLM with from macOS:
sysctl net.inet.tcp
Then it recommends next settings:
sudo sysctl -w net.inet.tcp.sendspace=2097152 # 2 MB default send
sudo sysctl -w net.inet.tcp.recvspace=8388608 # 8 MB default recv
sudo sysctl -w net.inet.tcp.autosndbufmax=16777216 # 16 MB max send
sudo sysctl -w net.inet.tcp.autorcvbufmax=33554432 # 32 MB max recv
sudo sysctl -w net.inet.tcp.autosndbufinc=131072 # grow send buffer aggressively
sudo sysctl -w net.inet.tcp.local_slowstart_flightsize=30
sudo sysctl -w net.inet.tcp.bg_ss_fltsz=20 # YouTube is background traffic
To make it permanent:
In /etc/sysctl.conf:
sudo tee /etc/sysctl.conf > /dev/null <<EOF
net.inet.tcp.sendspace=2097152
net.inet.tcp.recvspace=8388608
net.inet.tcp.autosndbufmax=16777216
net.inet.tcp.autorcvbufmax=33554432
net.inet.tcp.autosndbufinc=131072
net.inet.tcp.local_slowstart_flightsize=30
net.inet.tcp.bg_ss_fltsz=20
EOF