El Capitan was on system. You could browse some sites fine then BAM...the browser loading bar would cross the browser (Safari AND Chrome) and you would be unable to browse any further. What I tried? So updated the system to Sierra and then migrated data and settings. Exact same problem. You could browse the internet effortlessly using Safari or Chrome for 20 minutes then BAM you can no longer browse. Here is what else I tried: - 2nd laptop was connected to router - constant speedy internet. - All networking devices were removed from Network Settings and re-added - The ISP's DNS was changed to Google's DNS - Went to router - different SSID and channel applied - same problem - HDD tested fine. Hopefully someone here came across a similar problem.