Intercepting HTTP Traffic

Proxy.app allows you intercept both HTTP requests and responses and modify their data in transit. To start intercepting follow these steps.

Step 1

Set the proxy in interception mode - There are several operation modes. In order to switch between the different proxy modes use key combination ⌘T or use the toolbar toggle.

Screenshot 01

Step 2

Modify request data - While Proxy.app is set in interception mode, requests to and from the proxy will be available for modification. A popup window will be presented when an event is triggered. You can modify the request data from the request editor view. Once you are happy with the result click on the Post button.

Screenshot 02

Step 3

Modify response data - Next, you can modify the response from the server. This view works exactly the same as the previous step. Modify the data they way you want it and click on the Post button.

Screenshot 02

Things To Keep In Mind

  • The proxy toggle is constantly available even when you are in interception mode. This is an important thing to remember because there may be situations where you may want to turn off interception while editing the current request or response.
  • In order to flush all currently intercepted requests and responses use the Post All button. You can also discard individual request and responses or all of them by using the Discard and Discard All buttons respectively.
  • You can exit the interception dialog by clicking on the Close button or by pressing ESC key on your keyboard.
  • Keep in mind that the proxy is non-buffering and requests and responses are not scheduled in any particular order. This means that if you spend too much time editing the data the request or the response may timeout and therefore it may not get delivered to its destination. It is recommended to enable longer timeout for the applications you want to test in order to avoid these situations.