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Jazzer

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Spec score 8.6 #4 of 26 in Fuzz Testing Software

What it is

Jazzer is a free, coverage-guided fuzzer for JVM applications, running in-process and based on libFuzzer. It supports Java, Kotlin, Scala, and Clojure targets, as well as JNI and native libraries. With JUnit 5.9.0 or newer, fuzz tests can run alongside regular unit tests. The @FuzzTest annotation lets Jazzer generate and mutate method inputs, including primitives, strings, arrays, and standard library classes. JUnit fuzz tests can use saved crashing inputs in regression mode or generate and mutate inputs to explore coverage. Built-in sanitizers detect Java security issues such as SSRF, file path traversal, and OS command injection, and provide feedback to guide fuzzing. The README documents use with Maven, Gradle, and Bazel. Jazzer can also run as a standalone binary or through its Java main class. Supported systems are Linux x86_64 and arm64, macOS 12 or newer on x86_64 and arm64, and Windows x86_64. The jazzer-junit package is available on Maven Central, and the repository identifies the project as licensed under Apache-2.0.

Spec sheet

What it does
Jazzer is an in-process, coverage-guided fuzzer for JVM applications, built on libFuzzer techniques.Read 15 Oct 2026 · github.com
Purpose
Jazzer is a coverage-guided, in-process fuzzer for the JVM based on libFuzzer.Read 29 Sep 2026 · github.com
License
The repository identifies Jazzer as Apache-2.0 licensed.Read 15 Oct 2026 · github.com
Headquarters
Bonn, GermanyRead 28 Sep 2026 · github.com
Bug detectors
Built-in sanitizers detect Java security issues including SSRF, file path traversal, and OS command injection, and provide feedback to guide fuzzing.Read 29 Sep 2026 · github.com
BugDetectors API
The public BugDetectors API lets code configure selected detectors, including SSRF and path-traversal checks.Read 15 Oct 2026 · codeintelligencetesting.github.io
Build integrations
Supported build workflows include Maven, Gradle and Bazel, with official rules_fuzzing support for Bazel.Read 15 Oct 2026 · github.com
Build tools
The README documents use with Maven, Gradle, and Bazel, including support through rules_fuzzing.Read 29 Sep 2026 · github.com
Company founding
LinkedIn lists Code Intelligence as founded in 2017.Read 15 Oct 2026 · linkedin.com
Company funding record
Crunchbase shows Code Intelligence with four funding rounds and a Series A led by Tola Capital, while amounts are withheld.Read 15 Oct 2026 · crunchbase.com
Company headquarters
LinkedIn lists Code Intelligence's headquarters in Bonn, North Rhine-Westphalia, Germany.Read 15 Oct 2026 · linkedin.com
Company legal name
Crunchbase identifies the maker as Code Intelligence GmbH.Read 15 Oct 2026 · crunchbase.com
Company size
LinkedIn places Code Intelligence in the 51-200 employee range.Read 15 Oct 2026 · linkedin.com
Configuration
Settings can be supplied through defaults, manifest attributes, environment variables, system properties, JUnit properties or CLI flags.Read 15 Oct 2026 · github.com
Corpus handling
New-coverage inputs are stored in generated corpus directories and failures are stored in inputs directories.Read 15 Oct 2026 · github.com
Coverage feedback
The tool instruments JVM bytecode and uses coverage feedback to guide input mutations.Read 15 Oct 2026 · google.github.io
Crash minimization
The standalone tool includes an option to minimize a crashing input to a smaller reproducer.Read 15 Oct 2026 · github.com
Distribution
The jazzer-junit package is available on Maven Central and the README says it is signed with a published key.Read 29 Sep 2026 · github.com
Fuzzing mode
Setting JAZZER_FUZZ to a non-empty value enables active fuzzing and input mutation.Read 15 Oct 2026 · codeintelligencetesting.github.io
FuzzTest annotation
Developers mark fuzz methods with @FuzzTest, which supports generated parameters and JUnit execution.Read 15 Oct 2026 · codeintelligencetesting.github.io
Independent research limitation
A 2026 paper reports that its GONDAR system found four times as many vulnerabilities as Jazzer on evaluated Java benchmarks.Read 15 Oct 2026 · arxiv.org
Independent research result
A 2026 study reports that its generated harnesses achieved a median 26% coverage improvement over OSS-Fuzz baselines and exceeded Jazzer AutoFuzz by 5% in package-scope coverage.Read 15 Oct 2026 · arxiv.org
Input generation
The @FuzzTest annotation lets Jazzer automatically generate and mutate method parameter inputs, including primitives, strings, arrays, and standard library classes.Read 29 Sep 2026 · github.com
JUnit integration
Jazzer integrates with JUnit 5.9.0 or newer through the jazzer-junit dependency.Read 15 Oct 2026 · github.com
Limit: open issues
The public issue tracker includes reports about Android builds, JDK 25 segmentation faults, BigInteger generation stalls and offline instrumentation failures.Read 15 Oct 2026 · github.com
Maven artifact
Maven Central lists com.code-intelligence:jazzer version 0.30.0 and identifies it as Apache-2.0 software.Read 15 Oct 2026 · central.sonatype.com
Mutation framework
The API exposes annotations and mutators for ranges, lengths, sizes, fixed value pools, protocol buffers and generated objects.Read 15 Oct 2026 · codeintelligencetesting.github.io
Native-library support
Advanced documentation states that Jazzer can fuzz native libraries loaded by the JVM.Read 15 Oct 2026 · github.com
Notable news: OSS-Fuzz
Google's OSS-Fuzz useful-links page records the Java fuzzing integration announcement on 2021-03-10.Read 15 Oct 2026 · google.github.io
OSS-Fuzz
Code Intelligence and Google have brought support for Java, Kotlin, and other JVM languages to Google's OSS-Fuzz project.Read 29 Sep 2026 · github.com
OSS-Fuzz availability
Google's JVM integration guide says Jazzer is preinstalled in OSS-Fuzz base images and works at bytecode level for JVM languages.Read 15 Oct 2026 · google.github.io
OSS-Fuzz engine limits
OSS-Fuzz documents libFuzzer as the only supported engine for JVM projects and lists AddressSanitizer and UndefinedBehaviorSanitizer as supported sanitizers there.Read 15 Oct 2026 · google.github.io
OSS-Fuzz input API
Google's guide documents Jazzer's FuzzedDataProvider for converting raw bytes into Java primitive and string values.Read 15 Oct 2026 · google.github.io
OSS-Fuzz reporting
OSS-Fuzz's Fuzz Introspector can generate Java reports showing reachability, coverage and possible fuzzing blockers.Read 15 Oct 2026 · google.github.io
Parallel fuzzing
Jazzer supports libFuzzer-style fork and jobs options for parallel execution.Read 15 Oct 2026 · github.com
Platform support
The README lists Linux x86_64 and arm64, macOS 12+ x86_64 and arm64, and Windows x86_64 as supported platforms.Read 29 Sep 2026 · github.com
Regression mode
JUnit integration replays saved crashing inputs as regression tests by default.Read 15 Oct 2026 · github.com
Repository activity
MvnRepository lists 29 published Jazzer versions and six reported users of the artifact.Read 15 Oct 2026 · mvnrepository.com
Run modes
JUnit fuzz tests can run in regression mode using saved crashing inputs or fuzzing mode to generate and mutate inputs for new coverage.Read 29 Sep 2026 · github.com
Sanitizer configuration
The README says SSRF and file path traversal sanitizers can be configured at runtime through BugDetectorsAPI.Read 29 Sep 2026 · github.com
Sanitizers
Built-in detectors cover issues including SSRF, path traversal, command injection and insecure deserialization patterns.Read 15 Oct 2026 · github.com
Standalone execution
Jazzer can run through its Java main class or a downloaded platform binary.Read 15 Oct 2026 · github.com
Standalone use
Jazzer can run standalone as a binary downloaded from GitHub release archives or through its Java main class.Read 29 Sep 2026 · github.com
Supported operating systems
The repository lists Linux x86_64 and arm64, macOS 12 or newer on x86_64 and arm64, and Windows x86_64.Read 15 Oct 2026 · github.com

Plans and prices

Jazzer Free Coverage-guided, in-process fuzzing for the JVM · Linux x86_64 and arm64, macOS 12+ x86_64 and arm64, Windows x86_64 Read 29 Sep 2026 · github.com
Jazzer open-source Free JVM fuzzing · local execution · Apache-2.0 licensed Read 15 Oct 2026 · github.com

Every Jazzer plan and price →

Strong points and limits

Strong points

  • Coverage guidance directs fuzzing toward new paths.
  • JUnit integration supports regular and fuzz tests.
  • Can reuse saved crashing inputs in regression mode.
  • Built-in sanitizers detect several Java security issues.
  • Available at no cost under Apache-2.0.

Limits

  • JUnit integration requires version 5.9.0 or newer.
  • Windows support is listed for x86_64 only.
  • macOS support is listed for version 12 or newer.

Who it suits

Jazzer suits developers testing JVM applications and related native libraries, particularly those using JUnit and Maven, Gradle, or Bazel. It is available for specified Linux, macOS, and Windows architectures.

Verdict

Jazzer brings coverage-guided fuzzing and security sanitizers into JVM testing workflows. Check the listed operating system and architecture requirements, and the JUnit version if using its test integration.

Where Specifiction places it

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