Jazzer

Free#7 of 25 in Fuzz Testing Software

Jazzer: A free, open-source JVM fuzzer with strong CI and build-tool integration. Ranked #7 of 25 in Fuzz Testing Software by our editors (8.2/10); pricing: Free plan; best for JVM application and library fuzzing.

8.2/10Editor score

Visit Jazzer

Jazzer8.2 Visit Jazzer

At a glance

Editor score
8.2 / 10
Pricing
Free plan
Best for
JVM application and library fuzzing
Free plan
Yes
Paid from
Free
Input generation methods
mutation, generation
Facts checked
20 Sep 2026

Where it wins
- Coverage-guided fuzzing with automatic input generation and mutation
- JUnit 5, Maven, Gradle, and Bazel integrations
- Crash reproduction, minimization, sanitizers, and OSS-Fuzz support
Where it doesn't
- Primarily focused on JVM ecosystems
- Execution is local rather than hosted
- Closed-source usage requires contacting Code Intelligence

Our verdict on Jazzer

Jazzer is an open-source, coverage-guided, in-process fuzzer for the Java Virtual Machine. It is suited to developers and security teams testing JVM applications and libraries written in Java, Kotlin, Scala, or Clojure, including targets that use JNI or native libraries. The tool runs on Windows, macOS, and Linux, and its free model makes it particularly relevant for open-source projects. Its JVM focus is clear: Jazzer instruments JVM bytecode for coverage feedback, generates and mutates inputs, and can run through a standalone binary or common development workflows.

The strongest fit is its integration with existing JVM testing and build environments. JUnit 5 support connects fuzzing with a familiar testing framework, while Maven, Gradle, and Bazel support can place fuzzing within established build processes. Jazzer also supports CI workflows and OSS-Fuzz integration, giving teams options for local execution and larger-scale open-source testing. Security sanitizers and bug detectors extend the workflow beyond input discovery, while stored crash inputs, generated Java reproducers, and crash minimization help turn findings into reproducible issues.

According to the published product details, Jazzer is free for open-source projects and open source itself. Closed-source users are directed to contact Code Intelligence. The main trade-off is scope: this is a focused JVM fuzzer rather than a broad, multi-language platform, and its execution model is local. Choose Jazzer when JVM coverage guidance, in-process execution, Java reproducer generation, and integrations with JUnit or JVM build tools are priorities. Consider another option when you need a hosted execution environment or fuzzing centered outside JVM ecosystems.

Your product? Our editors can test Jazzer in depth and publish a review, labelled as paid · from $149/mo →

Jazzer pricing

Plans Free planFree Free to use — no paid tier required for the core job.

See plans on github.com

Jazzer fact sheet

Free plan	Yes
Paid from	Free
Input generation methods	mutation, generation
Target types	JVM applications, Java, Kotlin, Scala, Clojure, JNI/native libraries
Coverage guidance	Yes
Crash triage	Yes
Execution mode	Local
Supported languages	Java, Kotlin, Scala, Clojure
CI/CD support	Yes
Deployment	Self-hosted
Platforms	Windows, macOS, Linux
Support	Docs, Community
Built for	Solo, Small business, Mid-market, Enterprise (editorial estimate)
Integrations	5 integrations: JUnit, Maven, Gradle, Bazel, OSS-Fuzz
Pricing	Free plan
Website	github.com
Facts checked	20 Sep 2026

Jazzer integrations

Jazzer lists 5 integrations on its own site.

JUnit
Maven
Gradle
Bazel
OSS-Fuzz

Alternatives to Jazzer

See all Jazzer alternatives →

Jazzer vs the competition

Compare Jazzer with any tool side by side →

Used Jazzer? Be the first to review it

The editor score above is our own research. What this page doesn't have yet is a reader's view — what you used Jazzer for, what worked and what didn't. No stars are seeded and no review is paid for; an editor reads every one before it appears.

Write a reviewTwo minutes · verified accounts only · read by an editor before it appears

Reviews come only from verified accounts. Sign in or create an account first — your e-mail is never shown.

Title

Your review

0 characters · at least 80, up to 3,000

Pros (optional · one per line)

Cons (optional · one per line)

Your name (shown with your review)

Role (optional)

Company (optional)

How long have you used it?

I've used Jazzer myself and this is my honest opinion — nobody paid or asked me to write it.

Posted from your verified account. Reviews appear after an editor reads them, usually within two working days.

Featured on iTechGuides

Jazzer is listed in our Fuzz Testing Software directory. Add the badge to your site — it links back to this page.

<a href="https://www.itechguides.com/products/jazzer/"><img src="https://www.itechguides.com/best/badge/jazzer.svg" alt="Featured on iTechGuides" width="230" height="46"></a>

Reviewed by iTechGuides Editors · Editorial team · Updated Oct 2026

Advertiser disclosure: iTechGuides is reader-supported. Vendors can pay for top positions in our rankings and for a place on other products' pages, and we may earn a commission when you click some links. Bought places stand at the number bought; this page and our disclosure say so. Paying vendors may get a fuller, more detailed review from our editors, and that review can change their score. How we rank.

Last updated 7 Oct 2026 · How we research and update