Book-Writing: Just Do It!

Sadly, you’re unlikely to get wealthy by writing a book. You should definitely write one anyway. My Background People I respect suggest you shouldn’t write (or buy) books on specific technologies, going so far as to say that writing a book was on their top-10 lists of life regrets. Top-10… whoa! As a consequence, whenContinue reading “Book-Writing: Just Do It!”

Repairing Corrupt ZIP Files

Fiddler’s default file format is the SAZ Format, which is just a ZIP file with a particular structure. Unfortunately, sometimes users’ SAZ files get corrupted due to failing disks or incomplete downloads, and when this happens, Fiddler can no longer open them. Because Fiddler uses a standard ZIP file, surely a good ZIP reader willContinue reading “Repairing Corrupt ZIP Files”

Reset Fiddler’s HTTPS certificates

I’ve made changes to the latest versions of Fiddler to improve the performance of certificate creation, and to avoid problems with new certificate validation logic coming to Chrome and Firefox. The biggest of the Fiddler changes is that CertEnroll is now the default certificate generator on Windows 7 and later. Unfortunately, this change can causeContinue reading “Reset Fiddler’s HTTPS certificates”

What’s New in Fiddler 4.6.0.7

TLDR? – Get the newest Fiddler here. We’re performing a staged rollout of this build; it won’t be on autoupdate until next week. Under the Hood As mentioned in our notes about the Fiddler 4.6 release, we’ve started taking a very close look at Fiddler’s performance. Fiddler’s use of the CPU, system memory, and theContinue reading “What’s New in Fiddler 4.6.0.7”

Viewing HTTPS Handshakes in Fiddler

You can easily use Fiddler to evaluate what algorithms a client is using to connect to a HTTPS server in Fiddler. First, adjust Fiddler’s configuration using Tools > Fiddler Options to enable capture of CONNECT tunnels but disable decryption: Disabling decryption is necessary because Fiddler decrypts traffic using a HTTPS man-in-the-middle technique, which means thatContinue reading “Viewing HTTPS Handshakes in Fiddler”

Fiddler and Brotli

Regular readers of my blog know how excited I am about Google’s new open compression engine, Brotli. Support is in Firefox 44 Nightly already and is expected for other browsers. Because Brotli is used inside the WOFF2 font format, many clients already have the compression code and just need to expose it in a newContinue reading “Fiddler and Brotli”

Fiddler Certificate Generators

Fiddler and FiddlerCore offer three different choices for generating interception certificates: MakeCert CertEnroll Bouncy Castle If you’re so inclined, you can even write your own certificate generator (say, by wrapping OpenSSL) and expose it to Fiddler using the ICertificateProvider3 interface. On Windows, Fiddler includes the MakeCert and CertEnroll certificate generators by default; you can downloadContinue reading “Fiddler Certificate Generators”

What’s New in Fiddler 4.6

Telerik Fiddler version 4.6 (and v2.6 targeting .NET2) is now available for download. The new version includes several new features and dozens of tweaks and bugfixes, described in this article. View > Tabs Menu The new View > Tabs menu offers a list of tabs that are hidden by default. The Preferences command displays aContinue reading “What’s New in Fiddler 4.6”

API Testing with Telerik Fiddler

Fiddler has long been the tool of choice for developers and testers who are building and verifying APIs exposed over HTTP(S). In this post, we’ll explore the existing features Fiddler offers for API Testing and announce new capabilities we’ve released in Fiddler 2.6/4.6. Composing API Calls The Composer tab enables the authoring of arbitrary HTTP(S)Continue reading “API Testing with Telerik Fiddler”