ClusterFuzz vs Schemathesis
ClusterFuzz
google.github.ioSchemathesis
schemathesis.ioSide by side
| Figure | ClusterFuzz | Schemathesis |
|---|---|---|
| Price from | Free | Free |
| Free plan | Yes | Yes |
| Free trial | — | — |
| Open source | — | — |
| Web | Yes | — |
| Windows | Yes | Yes |
| macOS | Yes | Yes |
| Linux | Yes | Yes |
| Self-hosted | Yes | Yes |
| Plans published | 1 | 1 |
| Spec score · Fuzz Testing Software | 8.9 (#2) | 7.5 (#16) |
| Authentication | ClusterFuzz supports various authentication providers using Firebase. | It supports Bearer tokens, Basic authentication, and API keys, with environment variable substitution and Python hooks for dynamic flows. |
| Integrations | The overview lists Monorail and Jira as example issue trackers and Firebase for authentication; the architecture page says Monorail is currently the only supported bug tracker. | The maker lists a GitHub Action, Docker image, pip or uvx installation, and pytest integration. |
| License | The ClusterFuzz repository is published under the Apache-2.0 license. | The project repository states that Schemathesis is licensed under the MIT license. |
| Purpose | ClusterFuzz is scalable fuzzing infrastructure that finds security and stability issues in software. | Schemathesis generates property-based tests from OpenAPI and GraphQL schemas to find API bugs. |
| Support | Users can file a GitHub issue to ask questions, request features, or ask for help. | The maker directs users to Discord for technical support, configuration questions, bug reports, and integration examples. |
Plans
In their own words
ClusterFuzz
ClusterFuzz is open-source infrastructure for finding security and stability problems in software through fuzzing. It supports coverage-guided engines libFuzzer, AFL++, and Honggfuzz, alongside blackbox fuzzing. Its workflow can find crashes, group duplicates, minimize testcases, use bisection to locate regressions, and verify fixes. It can also file, triage, and close bugs automatically. Google uses ClusterFuzz across its products and as the fuzzing backend for OSS-Fuzz. The system is designed to run on clusters of any size; Google’s instance runs on 30,000 VMs. Production deployments use Google Cloud services, including App Engine, Cloud Storage, Cloud Datastore, Cloud Pub/Sub, BigQuery, and Stackdriver Logging and Monitoring. Local instances are supported on Linux and macOS, with some BigQuery- and Stackdriver-dependent features disabled. Although the overview mentions Monorail and Jira as examples, the architecture currently supports only Chromium-hosted Monorail. The software runs on Linux, macOS, and Windows and is licensed under Apache-2.0. Its listed price is free.
Schemathesis
Schemathesis generates property-based tests from OpenAPI and GraphQL schemas to help engineers find API bugs. Its cases probe boundary values, type mismatches and constraint violations, and it validates API responses against the OpenAPI specification. For multi-step workflows, it chains operations using links inferred from a schema. During a run, it can learn validation rules, resource IDs and authentication requirements from server responses, then reuse them. Users can add Python checks for business rules alongside built-in checks. It supports OpenAPI 2.0, 3.0, 3.1 and 3.2, plus GraphQL schemas. Authentication options include Bearer tokens, Basic authentication and API keys, with environment variable substitution and Python hooks for dynamic flows. Integrations include a GitHub Action, Docker image, pip or uvx installation, and pytest. Reports can be exported as JUnit, VCR, HAR, NDJSON, JSON or Allure; failures can also be saved with curl commands for replay. The tool is self-hosted and licensed under MIT.