AFL++ vs Fuzzilli

AFL++ is a coverage-guided fuzzer that changes input and checks whether a target binary reaches a new execution path. Its afl-cc compiler supports LTO, LLVM and GCC_PLUGIN instrumentation. The project also lists collision-free coverage, AFLfast++ power schedules, MOpt mutators, laf-intel and redqueen. Documentation covers source-available software, binary-only targets, network services and GUI programs, with build options for source-only, binary-only or combined distributions. A Docker image supports x86_64 and arm64; its example mounts target source at /src. On Linux, the installation guide recommends LLVM 18 or newer and gives LLVM 14 as the minimum. macOS build guidance covers x86_64 and arm64, but afl-clang-lto, afl-gcc-fast and qemu_mode do not work there. Fuzzing can strain hardware, consume substantial memory or disk, and create heavy filesystem activity. AFL++ is available free under AGPL terms; modified versions offered as network services must provide users the corresponding source. A commercial license is listed at €20,000 a year.

Fuzzilli is a free, open-source, coverage-guided fuzzer for dynamic language interpreters. It represents test programs in FuzzIL, mutates them, and translates them to JavaScript for execution. Its mutators can change data flow or operation parameters, generate or splice code, and combine corpus programs. Components include a mutation fuzzer, script runner, corpus, environment, minimizer, evaluator, and lifter. A target engine runs repeated scripts in a read-eval-print-reset loop, resetting between cases; multiple instances can synchronize within a process or across machines over TCP. Listed target directories include JavaScriptCore, JerryScript, QuickJS, QtJS, Serenity, SpiderMonkey, V8, XS, Duktape, and njs. Setup requires compiling a supported engine with coverage instrumentation using clang 4.0 or later, then building Fuzzilli with Swift Package Manager. Docker and Google Compute Engine tooling are provided. The project supports Linux, macOS, and self-hosted use and identifies its license as Apache-2.0. Its repository says it is not an officially supported Google product. Contributions require a Contributor License Agreement and are reviewed through GitHub pull requests.