user firfox responsive design mode

[https://blog.nightly.mozilla.org/2016/11/07/simulate-slow-connections-with-the-network-throttling-tool/](https://blog.nightly.mozilla.org/2016/11/07/simulate-slow-connections-with-the-network-throttling-tool/)

or use a linux router in between, in case you need to throttle 3rd party applications

[https://stackoverflow.com/questions/614795/simulate-delayed-and-dropped-packets-on-linux](https://stackoverflow.com/questions/614795/simulate-delayed-and-dropped-packets-on-linux)