API Guard is a lightweight, privacy-first developer tool for comparing OpenAPI JSON specifications and detecting potential breaking changes before they reach production.

Features:

• Compare old and new OpenAPI specifications

• Detect removed endpoints and HTTP methods

• Detect removed or newly required parameters

• Detect parameter type changes

• Detect added and removed response codes

• Detect request bodies becoming required

• Generate realistic mock JSON responses from OpenAPI schemas

• Works entirely in the browser

• No backend, API key, or external service required

• Responsive design for desktop and mobile

Perfect for developers, API teams, SaaS builders, and agencies that need a simple API compatibility checker they can customize and integrate into their workflow.