Excerpt from readme:
Original AFL code written by Michal Zalewski <email@example.com>
Windows fork written and maintained by Ivan Fratric <firstname.lastname@example.org>
Copyright 2016 Google Inc. All Rights Reserved.
[…] Unfortunately, the original AFL does not work on Windows due to very *nix-specific design (e.g. instrumentation, forkserver etc). This project is a fork of AFL that uses different instrumentation approach which works on Windows even for black box binary fuzzing. […] The WinAFL approach: Instead of instrumenting the code at compilation time, WinAFL relies on dynamic instrumentation using DynamoRIO to measure and extract target coverage. This approach has been found to introduce an overhead about 2x compared to the native execution speed, which is comparable to the original AFL in binary instrumentation mode. To improve the process startup time, WinAFL relies heavily on persistant fuzzing mode, that is, executing multiple input samples without restarting the target process. This is accomplished by selecting a target function (that the user wants to fuzz) and instrumenting it so that it runs in a loop. […]