Using Fiddler for Mobile HTTPS Capture, Mocking, and Breakpoint Debugging

Mobile testers often need to capture packets, mock data, and throttle traffic; Fiddler is a powerful tool for these tasks, but it can present challenges that this article addresses.

HTTPS Capture Setup – Enable Tools → Options → HTTPS , check "Capture HTTPS CONNECTs", "Decrypt HTTPS traffic" and "Ignore server certificate errors", then confirm the trust prompt.

To capture HTTPS from a phone, install the FiddlerRoot certificate on the device by navigating to the computer’s IP and port in the phone’s browser, downloading the certificate, and trusting it in Settings → General → About → Certificate Trust Settings (iPhone).

Using Fiddler UI – The left pane lists requests; clicking a request shows request and response details, with tabs for Raw, Auth, Cookies, etc. Requests can be saved as .saz files for sharing.

Mocking with AutoResponder – Select a request, click the AutoResponder tab, add a rule, and choose match type (string, exact, regex). Enable the rule and optionally redirect to a local file or delay the response.

Breakpoints – Global breakpoints pause all traffic (Rules → Automatic Breakpoint → before requests). Individual breakpoints can be set via the command line (e.g., bpu https://example.com for before‑response). Use "Run to Completion" after editing.

By following these steps, testers can effectively capture HTTPS traffic, mock responses, and manipulate requests on mobile devices using Fiddler.