A binary format can help tremendously with fast web loading:

1. Code size can be significantly smaller, reducing download time (even with gzip; tests show a 30% win).

2. Parse times for a binary format can be much faster than for code as text, by a very large margin.

not worth the jump from open to close... a large margin when most pages already load almost instantly will go unnoticed by most people.

I think that you would see a much bigger performance increase if websites would not load resources from 10 different domains for serving a single web page (you have a much higher chance of getting some unforeseen delay from one of those hosts).

Parse time is basically free with WebAssembly