# LibAFL

LibAFL is a Rust library (and crate ecosystem) that ships *fuzzer parts* instead of *a fuzzer*. Stages, mutators, observers, feedbacks, schedulers, and corpora are all traits; you compose them into the fuzzer your target needs. The project came out of the AFL++ team and the AFLNet/CmpLog research lines, aiming to make it cheap to build domain-specific fuzzers that aren't AFL-shaped.

The architectural bet is that real-world fuzzing has too many target shapes (kernel, hypervisor, network, structured-input, grammar, differential, multi-target) for one binary's command-line flags to cover, so the right abstraction is library, not tool.

Used by:

- [[gosentry-go-fuzzing-fork|gosentry]] as the engine underneath a forked Go toolchain
- AFL++ as its experimental rewrite path
- Various academic and industry research fuzzers

## Relation to grammar / structure-aware fuzzing

LibAFL doesn't ship a grammar engine itself; tools built on it (gosentry, others) typically pull in [[grammar-based-fuzzing|Nautilus]] for grammar mode and the [[structure-aware-fuzzing]] decoder pattern for typed inputs.