Loading cached JS can still be very slow. https://www.webperf.tips/tip/cached-js-misconceptions/ https://www.webperf.tips/tip/cached-js-misconceptions/ has a go

Loading cached JS can still be very slow. https://www.webperf.tips/tip/cached-js-misconceptions/ https://www.webperf.tips/tip/cached-js-misconceptions/ has a good explanation of the bottlenecks involved. > Subsequent reloads from browser cache it's up barely long enough to notice. Are you measuring the time on your personal machine, or a machine that represents what your typical visitor is using? If you're using a recent Macbook, that's going to have very different performance characteristics than, say, an old Android phone. Something that's instantaneous on a Macbook could take ages on an old Android.