Slow download speed via Web browser on macOS Mojave
Your Internet connection speed alone doesn't determine the download speed that you will get when fetching a file from a remote site. You Internet bandwidth determines the maximum speed that you get when transferring content from a remote computer.

The remote computer (download host) may also have upload bandwidth restrictions due to variety of reasons. The upload speed of the remote computer in-effect considered in addition with your download speed determines the transfer speed you get.

It appears that the site you are trying to download data from have such restriction in place. To alleviate, try using an alternate download mechanism available on the site, via a different protocol or a download mirror.



To verify if you are receiving speed advertised by your ISP in the installed Web Browsers, you can simply check with one of the Internet speed testing websites.