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Tech riderRev. 4 Oct 2026

Fuzzilli

Ch 087.1of 27 Fuzz Testing Software
  1. 1Runs onLinux, Mac, self-hosted
  2. 2CostsFree plan
  3. 3Input generation methodsmutation, generation, hybrid
  4. 4Target typesJavaScript programs and JavaScript engines/interpreters
  5. 5Coverage guidanceYes
  6. 6Crash triageYes
  7. 7Execution modehybrid
  8. 8Supported languagesJavaScript
8 lines stated Written from the maker's own pages: github.com
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Overview

Fuzzilli is ranked #8 of 27 in fuzz testing software on Specifiction. It runs on Linux, macOS, Self-hosted. There is a free plan.

Fuzzilli plans and pricing

All plans
Fuzzilli Free Apache-2.0 licensed source code · requires building the fuzzer and a supported, instrumented JavaScript engine github.com · 4 Oct 2026

Compared on fuzz testing software

Input generation methods
mutation, generation, hybridgithub.com
Target types
JavaScript programs and JavaScript engines/interpretersgithub.com
Coverage guidance
Yesgithub.com
Crash triage
Yesgithub.com
Execution mode
hybridgithub.com
Supported languages
JavaScriptgithub.com
CI/CD support
Yesgithub.com

Facts

What it does
Fuzzilli is a coverage-guided fuzzer for dynamic language interpreters, built around a custom intermediate language called FuzzIL that can be mutated and translated to JavaScript.github.com · 3 Oct 2026
Mutations
Its documented mutators can change data flow, generate or splice code, combine corpus programs, and modify operation parameters.github.com · 3 Oct 2026
Fuzzer components
The listed components include a mutation fuzzer, script runner, corpus, environment, minimizer, evaluator, and lifter.github.com · 3 Oct 2026
Execution
Fuzzilli uses a read-eval-print-reset-loop mode in which a modified target engine accepts scripts over pipes or shared memory, executes them, resets, and waits for the next script.github.com · 3 Oct 2026
Scaling
Multiple instances can synchronize within one process or over a TCP-based protocol, allowing scaling across cores and machines.github.com · 3 Oct 2026
Supported targets
The repository lists JavaScriptCore, JerryScript, QuickJS, QtJS, Serenity, SpiderMonkey, V8, XS, Duktape, and njs target directories.github.com · 3 Oct 2026
Build requirements
The usage instructions call for compiling a supported JavaScript engine with coverage instrumentation using clang 4.0 or later, then building Fuzzilli with Swift Package Manager.github.com · 3 Oct 2026
Deployment
The project says Fuzzilli and supported engines can be built and run inside Docker and on Google Compute Engine.github.com · 3 Oct 2026
Cloud tooling
Its Cloud directory contains Docker scripts and files, Google Compute Engine setup and teardown scripts, and rudimentary crash triaging.github.com · 3 Oct 2026
Security results
The repository’s bug showcase lists security issues found with Fuzzilli across engines including WebKit/JavaScriptCore, SpiderMonkey, V8, Duktape, JerryScript, and Hermes.github.com · 3 Oct 2026
Security disclosure
The project asks users to send a short note, possibly with a CVE number, or open a pull request to have a vulnerability found with Fuzzilli considered for the bug showcase.github.com · 3 Oct 2026
License
The repository identifies its license as Apache-2.0.github.com · 3 Oct 2026
Support status
The repository states that Fuzzilli is not an officially supported Google product.github.com · 3 Oct 2026
Intended users
The project describes Fuzzilli as a tool for fuzzing dynamic language interpreters and invites patches and other contributions.github.com · 3 Oct 2026
Purpose
Fuzzilli is a coverage-guided fuzzer for dynamic language interpreters that mutates programs in FuzzIL and translates them to JavaScript.github.com · 4 Oct 2026
Mutation
Its mutators change program data flow, generate or splice code, combine corpus programs, and alter operation parameters.github.com · 4 Oct 2026
Core components
The fuzzer includes a mutation fuzzer, script runner, corpus, runtime environment, minimizer, evaluator, and lifter.github.com · 4 Oct 2026
Distributed fuzzing
Multiple instances can synchronize over a TCP-based protocol across machines or through dispatch queues within one process.github.com · 4 Oct 2026
Cloud deployment
The project provides Docker scripts and files for local or distributed fuzzing and scripts for setting up and tearing down distributed fuzzing on Google Compute Engine.github.com · 4 Oct 2026
Security findings
The repository’s bug showcase lists security-impacting bugs found with Fuzzilli in JavaScript engines including WebKit, SpiderMonkey, V8, Duktape, JerryScript, and Hermes.github.com · 4 Oct 2026
Google support
The repository states that Fuzzilli is not an officially supported Google product.github.com · 4 Oct 2026
Contributions
Project contributions require a Contributor License Agreement and are reviewed through GitHub pull requests.github.com · 4 Oct 2026

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