Sunday, December 19, 2010

Simulate a slow internet connection in web browsers (Internet Explorer, Firefox, Chrome etc)

You can easily simulate a slow internet connection, by using a tool called "fiddler".

Perhaps you are trying to debug a web application that is behaving strangely on other peoples computers (but is working fine on your own?!). Perhaps you wish to simulate a slow modem or a slow corporate VPN.

The fiddler is a web debugging proxy which logs all HTTP traffic between your computer and the internet. The fiddler has a setting to temporarily throttle your internet connection, to make your connection behave like a slow modem. The great thing about the fiddler is that it "automagically" sits in between all your web browsers and the internet, so it works with firefox, internet explorer, chrome etc etc.

Firstly you need to install "fiddler", just go to, download it and install it. It installs in seconds and has a getting started guide if you need it.

a screen shot of

Once you have the fiddler installed, open it and once loaded you should see a window similar to below. It should automatically act as a proxy, so if you browse to a website in any browser you should see it being logged in the fiddler.

the first page of the tool: fiddler. With a few HTTP requests logged.

To switch on "simulate slow modem speeds" mode in the fiddler (as illustrated in the screen shot below):

  1. If not already opened, open the fiddler.
  2. Click "Rules" on the top menu.
  3. Then go to "performance".
  4. Click "simulate modem speeds"
a screen shot illustrating how to turn on simulate modem speeds in the application called fiddler.

Now any web browser that is using fiddler (should be all web browsers by default), will temporary be slow (until you turn it off)

This is only scratching the surface of what the fiddler is useful for. There is plenty more information and an introductory video in the fiddler help section.


Bishnupriya said...

this is great o know, will apply immediately

Alex said...

Glad it came in useful Bishnu p.