OpenAPI Specification Viewer

A Clean, Client-Side Tool for Exploring API Documentation

What It Does

A lightweight viewer that lets you inspect OpenAPI specifications (YAML or JSON) directly in your browser — no uploads, no servers, just instant visualization of your API’s structure.

Benefits

  • Supports all OAS versions — 2.0 (Swagger), 3.0, and 3.1
  • Works with both formats — YAML and JSON parsed automatically
  • No data leaves your browser — everything processes client-side
  • Expandable sections — click to reveal parameters, schemas, and response details
  • Visual method badges — color-coded GET, POST, PUT, DELETE indicators
  • Quick navigation — sidebar tree for instant access to any endpoint or schema
  • Works offline — after first load, no internet required
  • Mobile-friendly — responsive design works on any device

How to Use

Upload a File:

  1. Go to julianreed.net/oas-viewer.html
  2. Click Upload File tab
  3. Choose your .yaml, .yml, or .json OAS file
  4. Navigate using the sidebar or scroll through endpoints

Paste Content:

  1. Go to julianreed.net/oas-viewer.html
  2. Click Paste Content tab
  3. Paste your OpenAPI specification
  4. Click Parse Specification
  5. Explore your API structure

Navigation:

  • Sidebar — click any endpoint or schema to jump directly to it
  • Expandable sections — click “Parameters”, “Request Body”, or “Responses” to reveal details
  • Method badges — color-coded for quick identification

Use Cases

  • Reviewing ISO 20022 payment schemas (pain.001, pacs.008, camt.054)
  • Quick API specification inspection during development
  • Client-facing API documentation without complex hosting
  • Offline API spec viewing for sensitive projects