Clone this repo:


  1. 3a32a50 [LPM] Tell people to use text format by default. by Jonathan Metzman · 5 days ago master
  2. d9b11f6 [unrar] Remove unrar_fuzzer by Jonathan Metzman · 5 weeks ago
  3. f7afc8c [libFuzzer] Docs: delete occurrences of max_len in libfuzzer_options. by Max Moroz · 5 weeks ago
  4. 8027711 [unrar] Add fuzzer by Jonathan Metzman · 6 weeks ago
  5. 83c2160 [libFuzzer] Fix condition so that seed corpus is built if specified by Jonathan Metzman · 6 weeks ago

libFuzzer in Chromium

go/libfuzzer-chromium (Googler only)

This directory contains integration between libFuzzer and Chromium. LibFuzzer is an in-process coverage-driven evolutionary fuzzing engine. It helps engineers to uncover potential security & stability problems.

Requirements: libFuzzer in Chromium is supported with Linux, Chrome OS, Mac, and Windows.

Integration Status

Fuzzer tests are well-integrated with Chromium build system and distributed ClusterFuzz fuzzing system. Cover bug:


  • Getting Started Guide walks you through all the steps necessary to create your fuzz target and submit it to ClusterFuzz.
  • Efficient Fuzzer Guide explains how to measure fuzz target effectiveness and ways to improve it.
  • Guide to libprotobuf-mutator (LPM) walks through the steps necessary to create a fuzz target that expects a protobuf as input (instead of a byte stream). In addition to fuzzing code that accepts protobufs, it can be used to fuzz code that requires multiple mutated inputs, or to generate inputs defined by a grammar.
  • ClusterFuzz Integration describes integration between ClusterFuzz and libFuzzer.
  • Reproducing Bugs describes how to reproduce bugs found by libFuzzer/AFL and reported by ClusterFuzz.
  • Fuzzing on Chrome OS describes how to write fuzzers for the non-browser parts of Chrome OS.
  • AFL Integration describes AFL's integration with Chromium and ClusterFuzz.
  • Reference contains detailed references for different integration parts.


  • ClusterFuzz Bugs - issues found and automatically filed by ClusterFuzz.
  • Manual Bugs - issues that were filed manually after running fuzz targets.
  • Pdfium Bugs - bugs found in pdfium by manual fuzzing.
  • OSS Trophies - bugs found with libFuzzer in open-source projects.

Blog Posts

Project Links