OpenAPI Viewer

The OpenAPI Viewer is a free browser-based tool that lets you paste OpenAPI 3.x or Swagger 2.0 specifications in JSON or YAML format and instantly visualize the API structure in a clean, readable layout. Reading raw JSON or YAML API specification files can be overwhelming, especially for large APIs with dozens of endpoints. This tool organizes endpoints by tags and displays each HTTP method (GET, POST, PUT, DELETE, PATCH) with intuitive color-coded badges for quick identification.

For each endpoint, you can see path parameters, query parameters, header parameters, request body content types, and response status codes with descriptions at a glance. The API title, version, description, and base URL are prominently displayed at the top for a quick overview of the specification. Complex schema definitions and $ref references are automatically resolved and rendered in human-readable format, showing parameter types and structures clearly without requiring manual schema lookup.

Whether you are a frontend developer checking backend API contracts, a backend developer reviewing API documentation, or a QA engineer verifying endpoint specifications, this tool streamlines your workflow. All parsing happens entirely within your browser, so internal API specs, private microservice definitions, and confidential endpoint documentation never leave your machine.

A built-in search and filter feature lets you quickly find specific endpoints even in large API specifications with hundreds of routes. Support for OpenAPI 3.0.x, 3.1.x, and Swagger 2.0 helps with APIs ranging from cloud-native microservices to traditional enterprise systems.

If your JSON specification is difficult to read, format it first with the [JSON Formatter](/en/dev/json-formatter/). To switch between YAML and JSON, use the [YAML JSON Converter](/en/dev/yaml-json-converter/). When you need to draft standalone schema definitions, use the [JSON Schema Generator](/en/dev/json-schema-generator/). For checking API responses and authentication headers, use the [HTTP Header Analyzer](/en/dev/http-header-analyzer/) as well.