Jazzer
Jazzer is a free, coverage-guided in-process fuzzer for JVM applications, based on libFuzzer.
What Jazzer is
Jazzer is a free, coverage-guided in-process fuzzer for JVM applications, based on libFuzzer. It supports targets written in Java, Kotlin, Scala, and Clojure, as well as JNI and native libraries. With JUnit 5.9.0 or newer, fuzz tests can be included alongside regular unit tests. The @FuzzTest annotation lets Jazzer generate and mutate inputs for method parameters such as primitives, strings, arrays, and standard library classes. JUnit fuzz tests can run in regression mode using saved crashing inputs or in fuzzing mode to explore for new coverage. Built-in sanitizers detect Java security issues such as SSRF, file path traversal, and OS command injection, and provide feedback to guide fuzzing. 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 are Linux x86_64 and arm64, macOS 12 or later on x86_64 and arm64, and Windows x86_64. The repository identifies Jazzer as licensed under Apache-2.0.
Good
- Works with JUnit 5.9.0 or newer.
- Supports Maven, Gradle, and Bazel.
- Regression mode can replay saved crashing inputs.
- Sanitizers detect several Java security issues.
- Free and licensed under Apache-2.0.
Watch out
- Windows support is listed for x86_64 only.
- macOS support is listed for version 12 and later.
- JUnit integration requires version 5.9.0 or newer.
Who it suits
Jazzer suits developers working on JVM applications who want local coverage-guided fuzzing, including teams using JUnit. It also supports projects targeting JNI or native libraries.
Verdict
Jazzer provides JVM fuzzing with JUnit integration, standalone operation, and security-focused sanitizers. Check the listed operating-system and JUnit requirements against your environment.
Plans and prices
From Jazzer's own pricing page, checked 29 Sep 2026.
| Plan | Price | What it gives you |
|---|---|---|
| Jazzer | Free | Coverage-guided, in-process fuzzing for the JVM · Linux x86_64 and arm64, macOS 12+ x86_64 and arm64, Windows x86_64 |
| Jazzer open-source | Free | JVM fuzzing · local execution · Apache-2.0 licensed |
The facts
Each one read from Jazzer's own pages, with the date it was checked.
What it does
- Bug detectors
- Built-in sanitizers detect Java security issues including SSRF, file path traversal, and OS command injection, and provide feedback to guide fuzzing.checked 29 Sep 2026
- BugDetectors API
- The public BugDetectors API lets code configure selected detectors, including SSRF and path-traversal checks.checked 15 Oct 2026
- Build integrations
- Supported build workflows include Maven, Gradle and Bazel, with official rules_fuzzing support for Bazel.checked 15 Oct 2026
- Build tools
- The README documents use with Maven, Gradle, and Bazel, including support through rules_fuzzing.checked 29 Sep 2026
- Configuration
- Settings can be supplied through defaults, manifest attributes, environment variables, system properties, JUnit properties or CLI flags.checked 15 Oct 2026
- Corpus handling
- New-coverage inputs are stored in generated corpus directories and failures are stored in inputs directories.checked 15 Oct 2026
- Coverage feedback
- The tool instruments JVM bytecode and uses coverage feedback to guide input mutations.checked 15 Oct 2026
- Crash minimization
- The standalone tool includes an option to minimize a crashing input to a smaller reproducer.checked 15 Oct 2026
- Distribution
- The jazzer-junit package is available on Maven Central and the README says it is signed with a published key.checked 29 Sep 2026
- Fuzzing mode
- Setting JAZZER_FUZZ to a non-empty value enables active fuzzing and input mutation.checked 15 Oct 2026
- FuzzTest annotation
- Developers mark fuzz methods with @FuzzTest, which supports generated parameters and JUnit execution.checked 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.checked 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.checked 15 Oct 2026
- Input generation
- The @FuzzTest annotation lets Jazzer automatically generate and mutate method parameter inputs, including primitives, strings, arrays, and standard library classes.checked 29 Sep 2026
- JUnit integration
- Jazzer integrates with JUnit 5.9.0 or newer through the jazzer-junit dependency.checked 15 Oct 2026
- License
- The repository identifies Jazzer as Apache-2.0 licensed.checked 15 Oct 2026
- Limit: open issues
- The public issue tracker includes reports about Android builds, JDK 25 segmentation faults, BigInteger generation stalls and offline instrumentation failures.checked 15 Oct 2026
- Maven artifact
- Maven Central lists com.code-intelligence:jazzer version 0.30.0 and identifies it as Apache-2.0 software.checked 15 Oct 2026
The company
- Company founding
- LinkedIn lists Code Intelligence as founded in 2017.checked 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.checked 15 Oct 2026
- Company headquarters
- LinkedIn lists Code Intelligence's headquarters in Bonn, North Rhine-Westphalia, Germany.checked 15 Oct 2026
- Company legal name
- Crunchbase identifies the maker as Code Intelligence GmbH.checked 15 Oct 2026
- Company size
- LinkedIn places Code Intelligence in the 51-200 employee range.checked 15 Oct 2026
- Headquarters
- Bonn, Germanychecked 28 Sep 2026
Alternatives to Jazzer
- 1
AFL++
Free planAndroidLinuxmacOSSelf-hosted7.2From €20,000 a year - 2
Mayhem
Free planWebAPILinuxmacOS7.0From $236 a month - 3
ClusterFuzz
Free planWebLinuxmacOSSelf-hosted6.8Free plan - 4
cargo-fuzz
Free planLinuxmacOSWindows6.7Free plan - 5
boofuzz
Free planAPILinuxSelf-hostedWindows6.4Free plan - 6
EvoMaster
Free planAPILinuxmacOSSelf-hosted6.4Free plan