Throttling

Throttling in Charles allows you to simulate different network conditions. You can change the available bandwidth, network utilisation, latency as well as change the MTU size. You can also enable this only for selected hosts, which is particularly useful for simulating a poor connection to a 3rd party (eg. Google is slow).

The settings for Throttling are available under Proxy > Throttling Settings, and you can turn it on/off under Proxy > Throttling.

You can also set Charles to throttle by default in Settings: Charles > Preferences > Startup and select ‘Start Throttling`.

Memory Usage

Charles can consume quite a lot of memory as it records all traffic passing through your network device. If you constantly find yourself being presented with warnings about Charles running out of memory, you can boost the Recording Size Limit under Proxy > Recording Settings. You can also limit the Recording History here.

You can display how much memory is being consumed by your current Charles session in Settings: Charles > Preferences > Show Memory Usage. When you restart Charles, the current memory usage will be displayed in Charles’ status bar on the right hand side.

Remote Mapping

I’m often required to do a lot of VM-based testing (damn you Internet Explorer) and it’s often a little tricky to set up a browser in the VM to connect to your local OSX server. For instance, if you simply setup a traffic redirect to http://localhost, then the VM’s browser will try and navigate to localhost on the VM, not your machine.

The better way to do this is to set up your Remote Mapping to point to your IP, not localhost. So go to Tools > Map Remote and Add a remote mapping. Then set the URL you’re trying to capture as your From setting, eg. http://my-test-website.com and the To setting as your current IP on your OSX machine, eg. http://192.168.0.10.

This way, when the VM’s browser makes the request, it actually fetches the URL from http://192.168.0.10.