Paste an OpenAPI 3 or Swagger 2 spec (YAML or JSON), browse endpoints, parameters, and schemas. All client-side, no upload.
Format, validate, and minify JSON data with syntax highlighting
Encode and decode Base64 strings
Generate and validate UUIDs (v4)
Test regular expressions with real-time matching
OpenAPI (formerly Swagger) is the industry-standard format for describing REST APIs in YAML or JSON. The full Swagger UI is heavy (~2 MB) and often online-only — privacy-sensitive when your spec contains internal endpoint names or unreleased features. The OpenAPI Viewer parses your spec entirely in your browser, groups endpoints by tag, and shows methods (color-coded GET/POST/PUT/DELETE/PATCH), parameters with location (query/path/header/cookie), request body content types, and response codes with descriptions. Works with both OpenAPI 3.0/3.1 and legacy Swagger 2.0. Paste a spec from an internal staging server or a confidential RFC — nothing is uploaded.
OpenAPI 3.x: detected via top-level "openapi" field Swagger 2.0: detected via top-level "swagger" field Format: YAML or JSON (auto-detected) Fields rendered: info, servers, paths (all 8 HTTP methods), parameters, requestBody, responses, components/schemas (count only)