Safari Web Inspector network throttling

Just found a way to do it without having to use a proxy like Charles:

1. Install XCode
2. Connect iPhone to mac via USB
3. Launch XCode
4. Access developer settings on iPhone
5. Use "Network Link Conditioner"

Longer blog post I wrote: Enable network throttling on iPhone in 5 steps

Hope this helps!

There is currently not a way to do that natively in Safari but you might try using something like Charles Proxy that can throttle your browser or system connection (win, mac, linux).