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Jazzer
Bonn, Germany
What it is
Jazzer is a free, coverage-guided fuzzer that runs in-process for JVM applications and is 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 sit alongside ordinary unit tests. The @FuzzTest annotation lets Jazzer generate and mutate method inputs, including primitives, strings, arrays and standard library classes. Tests can use saved crashing inputs in regression mode or fuzz for additional coverage. Built-in sanitizers flag Java security issues such as SSRF, file path traversal and OS command injection, with feedback to guide fuzzing. SSRF and file path traversal checks can be configured at runtime through BugDetectorsAPI. Jazzer works with Maven, Gradle and Bazel, and can run as a standalone binary or through its Java main class. The jazzer-junit package is available on Maven Central. Supported systems include Linux x86_64 and arm64, macOS 12 or later on both architectures, and Windows x86_64. The repository identifies the project as Apache-2.0 licensed.
For and against
For
- Coverage-guided fuzzing runs in-process.
- JUnit fuzz tests can accompany unit tests.
- Built-in sanitizers flag several Java security issues.
- Works with Maven, Gradle and Bazel.
- Free and licensed under Apache-2.0.
Against
- Windows support is limited to x86_64.
- macOS support requires version 12 or newer.
- JUnit integration requires version 5.9.0 or newer.
The verdict
Jazzer offers JVM fuzzing with JUnit integration, build-tool support and security-focused sanitizers. Check its listed operating-system architectures and JUnit version requirement against your environment.
Who it suits
Jazzer suits developers who want to fuzz JVM applications or native libraries and integrate fuzz tests with JUnit or common build tools. It also supports teams targeting Java, Kotlin, Scala or Clojure.
Plans and prices
Jazzer open-source
JVM fuzzing · local execution · Apache-2.0 licensed
Read 15 Oct 2026 · github.com
Jazzer
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
On the record
- Bug detectors
- Built-in sanitizers detect Java security issues including SSRF, file path traversal, and OS command injection, and provide feedback to guide fuzzing.github.com · read 29 Sep 2026
- BugDetectors API
- The public BugDetectors API lets code configure selected detectors, including SSRF and path-traversal checks.codeintelligencetesting.github.io · read 15 Oct 2026
- Build integrations
- Supported build workflows include Maven, Gradle and Bazel, with official rules_fuzzing support for Bazel.github.com · read 15 Oct 2026
- Build tools
- The README documents use with Maven, Gradle, and Bazel, including support through rules_fuzzing.github.com · read 29 Sep 2026
- Company founding
- LinkedIn lists Code Intelligence as founded in 2017.linkedin.com · read 15 Oct 2026
- Company funding record
- Crunchbase shows Code Intelligence with four funding rounds and a Series A led by Tola Capital, while amounts are withheld.crunchbase.com · read 15 Oct 2026
- Company headquarters
- LinkedIn lists Code Intelligence's headquarters in Bonn, North Rhine-Westphalia, Germany.linkedin.com · read 15 Oct 2026
- Company legal name
- Crunchbase identifies the maker as Code Intelligence GmbH.crunchbase.com · read 15 Oct 2026
- Company size
- LinkedIn places Code Intelligence in the 51-200 employee range.linkedin.com · read 15 Oct 2026
- Configuration
- Settings can be supplied through defaults, manifest attributes, environment variables, system properties, JUnit properties or CLI flags.github.com · read 15 Oct 2026
- Corpus handling
- New-coverage inputs are stored in generated corpus directories and failures are stored in inputs directories.github.com · read 15 Oct 2026
- Coverage feedback
- The tool instruments JVM bytecode and uses coverage feedback to guide input mutations.google.github.io · read 15 Oct 2026
- Crash minimization
- The standalone tool includes an option to minimize a crashing input to a smaller reproducer.github.com · read 15 Oct 2026
- Distribution
- The jazzer-junit package is available on Maven Central and the README says it is signed with a published key.github.com · read 29 Sep 2026
- Fuzzing mode
- Setting JAZZER_FUZZ to a non-empty value enables active fuzzing and input mutation.codeintelligencetesting.github.io · read 15 Oct 2026
- FuzzTest annotation
- Developers mark fuzz methods with @FuzzTest, which supports generated parameters and JUnit execution.codeintelligencetesting.github.io · read 15 Oct 2026
- Independent research limitation
- A 2026 paper reports that its GONDAR system found four times as many vulnerabilities as Jazzer on evaluated Java benchmarks.arxiv.org · read 15 Oct 2026
- 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.arxiv.org · read 15 Oct 2026
