Catch API bugs before your users do.

Schemathesis automatically generates thousands of test cases from your OpenAPI or GraphQL schema and finds edge cases that break your API.

Finding bugs that manual testing missed

# Test a demo API - finds real bugs instantly
uvx schemathesis run https://example.schemathesis.io/openapi.json
# Test your own API
uvx schemathesis run https://your-api.com/openapi.json

• 💥 500 errors that crash your API on edge case inputs
• 📋 Schema violations where your API returns different data than documented
• 🚪 Validation bypasses where invalid data gets accepted
• 🔗 Integration failures when responses don't match client expectations

⚠️ Upgrading from older versions? Check our Migration Guide for key changes.

Command Line:

uv pip install schemathesis
schemathesis run https://your-api.com/openapi.json

Python Tests:

import schemathesis
schema = schemathesis.openapi.from_url("https://your-api.com/openapi.json")
@schema.parametrize()
def test_api(case):
    case.call_and_validate()  # Finds bugs automatically

CI/CD:

- uses: schemathesis/action@v2
  with:
    schema: "https://your-api.com/openapi.json"

Used by teams at Spotify, WordPress, JetBrains, Red Hat and dozens other companies.

"Schemathesis is the best tool for fuzz testing of REST API on the market. We are at Red Hat use it for examining our applications in functional and integrations testing levels." - Dmitry Misharov, RedHat

📚 Complete documentation with guides, examples, and API reference.

• 💬 Discord community
• 🐛 GitHub issues

We welcome contributions! See our contributing guidelines and join discussions in issues or Discord.

Schemathesis is built on top of Hypothesis, a powerful property-based testing library for Python.

This project is licensed under the terms of the MIT license.