Configuring ZAP for API Testing

Effective API testing with ZAP begins with proper configuration tailored to API-specific requirements. Start by importing API definitions if available. ZAP supports OpenAPI (Swagger), WSDL, and GraphQL schema imports through the "Import" menu. These definitions provide ZAP with a comprehensive understanding of available endpoints, expected parameters, and data types. This automated import dramatically improves testing coverage compared to manual endpoint discovery.

# Example OpenAPI definition import
openapi: 3.0.0
info:
  title: Example API
  version: 1.0.0
servers:
  - url: https://api.example.com/v1
paths:
  /users/{userId}:
    get:
      parameters:
        - name: userId
          in: path
          required: true
          schema:
            type: integer
      responses:
        200:
          description: User details

Manual API exploration requires different techniques than traditional spidering. APIs don't have hyperlinks to follow, so discovery relies on documentation analysis, traffic observation, or intelligent guessing. Use ZAP's proxy to capture API traffic from mobile apps or thick clients. This passive discovery reveals undocumented endpoints and actual usage patterns. Configure your API client (Postman, cURL, or custom scripts) to route through ZAP's proxy for comprehensive traffic capture.

Context configuration for APIs requires special attention to data formats and content types. Configure ZAP to properly handle JSON, XML, or other API formats. Set appropriate Content-Type headers in scan policies. Define custom input vectors for API-specific parameters like query strings, path parameters, and request bodies. Enable "Inject plugin ID in header" to track which scanner rules trigger specific requests, aiding in false positive analysis.