Grizzly

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Grizzly is a modular general purpose browser fuzzing framework. The goal is to create a platform that can be extended via the creation of plug-ins to support multiple combinations of browsers and fuzzers. An Adapter is used to add support for a fuzzer and a Target to add support for a browser. Generated test cases are intended to be standalone and not require Grizzly.

Cross platform compatibility is available for Windows, Linux and MacOS. However not all features may be available.

For additional information please check out the wiki or the announcement.

Quick Start

Install the latest version from PyPI. For more details see getting started on the wiki.

python3 -m pip install grizzly-framework --upgrade

Fuzzing - Run the no-op test adapter to check everything is working.

grizzly <browser-binary> no-op

Reduce - Grizzly Reduce can reduce a test case.

grizzly-reduce <browser-binary> <testcase>

Replay - Grizzly Replay can replay a test case with different builds and debuggers.

grizzly-replay <browser-binary> <testcase>

Bugzilla is also supported by Grizzly Replay. Bugs can be replayed via a bug ID:

grizzly-replay-bugzilla <browser-binary> <bug_id>

Questions

Common questions can be found on the Q&A page. Questions can also be asked in the #fuzzing channel.

Please be sure you are using the latest version Grizzly before reporting issues.

Project links

Data verified by PyPI on Aug 20, 2026
Data provided by the project maintainers, verified at the time the release was uploaded to PyPI.

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Latest release

2 maintainers

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Credits

Author: Tyson Smith

Maintainer: Mozilla Fuzzing Team

GitHub Statistics

Data verified by PyPI on Aug 20, 2026
The GitHub source repository was provided by the project maintainers and verified by PyPI at the time of upload. Stars, forks, and open issues/PRs are derived from that repository and have not been independently verified.

License

Mozilla Public License 2.0 (MPL 2.0) (MPL 2.0)

Requires

Python >=3.10

Provides Extra

dev

Tags

firefox framework fuzz fuzzing test testing

Classifiers

Report project as malware

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