For general fuzzing terms, see the glossary from google/fuzzing project.

OSS-Fuzz specific terms


A scalable fuzzing infrastructure that is used for OSS-Fuzz backend. ClusterFuzz is also used to fuzz Chrome and many other projects. A quick overview of ClusterFuzz user interface is available on this page.

Fuzz Target

In addition to its general definition, in OSS-Fuzz a fuzz target can be used to reproduce bug reports. It is recommended to use it for regression testing as well (see ideal integration).

Job type

Or Fuzzer Build.

This refers to a build that contains all the fuzz targets for a given project, is run with a specific fuzzing engine, in a specific build mode (e.g. with enabled/disabled assertions), and optionally combined with a sanitizer.

For example, we have a “libfuzzer_asan_sqlite” job type, indicating a build of all sqlite3 fuzz targets using libFuzzer and ASan.


A project is an open source software project that is integrated with OSS-Fuzz. Each project has a single set of configuration files (example: expat) and may have one or more fuzz targets (example: openssl).


Or a testcase.

A test input that causes a specific bug to reproduce.


Fuzzers are usually built with one or more sanitizer enabled.

$ python infra/ build_fuzzers --sanitizer undefined json

Supported sanitizers:

Sanitizer Description
address (default) Address Sanitizer with Leak Sanitizer.
undefined Undefined Behavior Sanitizer.
memory Memory Sanitizer.
NOTE: It is critical that you build all the code in your program (including libraries it uses) with Memory Sanitizer. Otherwise, you will see false positive crashes due to an inability to see initializations in uninstrumented code.
coverage Used for generating code coverage reports. See Code Coverage doc.

Compiler flag values for predefined configurations are specified in the Dockerfile. These flags can be overridden by specifying $SANITIZER_FLAGS directly.

You can choose which configurations to automatically run your fuzzers with in project.yaml file (e.g. sqlite3).


ClusterFuzz supports fuzzing on x86_64 (aka x64) by default. However you can also fuzz using AddressSanitizer and libFuzzer on i386 (aka x86, or 32 bit) by specifying the $ARCHITECTURE build environment variable using the --architecture option:

python infra/ build_fuzzers --architecture i386 json