OpenAPI / Swagger Viewer

Upload or paste an API spec and explore every endpoint, parameter, schema and auth requirement — without leaving your browser.

Drop in any OpenAPI 3.x or Swagger 2.0 document (JSON or YAML) and the viewer maps the whole API: operations grouped by tag with their parameters, request bodies and response codes, the authentication each operation demands, every schema resolved out of $ref chains with generated sample values, and copy-ready cURL examples you can run straight from the terminal.

🔒 100% private — nothing is uploaded or stored. The spec is parsed and explored entirely in your browser. Internal endpoints, schema names and anything else sensitive in the document never leave this tab — no server round-trip, no logging, no saving.

1 · Load a spec

Or: 📄 Upload file Try:

2 · Overview

3 · Authentication

4 · Endpoints

5 · Schemas

Every $ref is resolved inline, so you see the real shape of each type. Click a schema to inspect it.

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6 · Export

Endpoint list (Markdown)

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Re-serialised from the parsed document — handy when you only had YAML.

OpenAPI vs Swagger — and where to find a spec

The two names get mixed up constantly, so here is the short version:

Swagger 2.0 (2014–2016) was the first widely-used REST API description format, driven by the Swagger UI project. Specs start with "swagger": "2.0", carry a single host/basePath/schemes triple, and keep types in definitions.
OpenAPI 3.x is the successor, now maintained by the OpenAPI Initiative (a Linux Foundation project). Specs start with "openapi": "3.0" or "3.1", support multiple servers with URL variables, move types to components.schemas, and describe request bodies properly via requestBody (which 2.0 could only fake with a body parameter). OpenAPI 3.1 additionally aligns with JSON Schema 2020-12.
Both describe the same thing — a machine-readable contract of endpoints, parameters, schemas and auth — so this viewer handles either. If a tool says “Swagger spec”, it usually means 2.0; “OpenAPI spec” means 3.x.

Where do specs come from?

FastAPI exposes one automatically at /openapi.json; many Spring and Express services ship /swagger.json or /v3/api-docs. Check the API docs page first — a link to the raw document is usually one click away.
Postman, Insomnia and similar clients can export an entire collection as an OpenAPI 3.x file from their export menu.
For your own projects, code generators (swagger-codegen / openapi-generator) produce a spec from annotations, or you maintain the YAML by hand — contract-first development means the spec is written before the endpoints are.

Once you have inspected an endpoint here, the API Request Builder helps you assemble and test the actual request, and the JSON Formatter & Validator is handy for tidying the documents you paste in.

Spot a bug or want a custom utility built? I'd love to hear from you. Get in touch
Luke Keam | techgeek.biz