Slow down connection for Browser for testing [duplicate]
Turn on developer mode and then go to 
network tab, you will be able to see the throttling option drop-down option, change the network type from there.See the screenshot.
New chrome browser has "Throttling" option in "Network" tab in Dev tools.Good Luck
If you are on a Mac, this might be of interest - it allows you to simulate different network conditions.
https://apple.stackexchange.com/questions/24066/how-to-simulate-slow-internet-connections-on-the-mac
See the second answer (and give credit for the answer) by Randy6T9
Speed Limit is a System Preferences pane for intentionally and selectively slowing down specific ports and domains