Common Fiddler Issues and Their Solutions

The author, with two years of testing experience, praises Fiddler for automatically configuring the browser proxy on launch and restoring settings on exit, but notes that colleagues often encounter capture problems.

1. Cannot capture HTTPS links The most common cause is the missing certificate. Download the certificate, trust it locally, and restart Fiddler to make the change effective.

2. Browser shows "target machine actively refused" First, check for host bindings; if present, ping the IP or telnet to the port to verify connectivity. If no host is bound, try restarting the system. If the error persists, it is a Fiddler configuration issue. When the error mentions "::1", it refers to the IPv6 loopback address. Solutions: add 127.0.0.1 localhost to the hosts file, or disable IPv6 in Options → General → Enable IPv6.

3. "Failed to register Fiddler as the system proxy" After upgrading to Windows 10, Fiddler may fail to set itself as the system proxy. The fix is to enable the "WinHTTP Web Proxy Auto-Discovery Service" (which may have been disabled during system optimization) and then restart the computer.

In summary, the author thanks the community for their shared solutions and invites readers to share any other unusual Fiddler issues they have encountered.