Zero Snippet

OpenAPI and Swagger viewer — YAML, JSON, paths, and schemas

Use this free OpenAPI viewer online to paste OpenAPI 3.x or Swagger 2.0 in YAML or JSON, then browse REST paths and HTTP methods, parameters and request bodies, responses, and reusable schemas (components.schemas or definitions). Everything runs in your browser—helpful when you review an API contract before implementation, compare versions with git, or explain an endpoint to a teammate without spinning up Swagger Editor. Pair exploration with our HTTP request builder for live calls and the API response formatter when you inspect JSON payloads next to the documented schema.

Paste OpenAPI (YAML or JSON)

Client-side parse—then browse paths, operations, and schemas.

Parse a valid OpenAPI 3.x or Swagger 2.0 document to browse paths and schemas.

Why use an OpenAPI or Swagger viewer?

OpenAPI is the industry-standard way to describe HTTP APIs: resources, methods, media types, security schemes, and examples in one machine-readable file. Teams publish interactive API documentation from the same artifact they use for codegen and contract tests. A dedicated Swagger viewer (Swagger was the earlier name; many people still search for it) helps you navigate that file when it is long, deeply nested, or split across repositories. This page focuses on read-only structure: you see parameters, bodies, and response maps aligned with how backends and gateways actually behave.

Unlike hosted documentation that may lag a release branch, pasting a local spec here lets you verify the exact YAML or JSON your pipeline emits. If you still author data in JSON first, run it through our JSON formatter to confirm brackets and commas; if your source lives in YAML, the YAML to JSON converter and JSON to YAML converter help you move between formats before you paste into this viewer.

OpenAPI 3.x vs Swagger 2.0 (quick guide)

Swagger 2.0 uses a top-level swagger: "2.0" field and stores models under definitions. OpenAPI 3.x introduces openapi: 3.x.x, first-class requestBody objects, explicit content maps per status code, and components for schemas, responses, parameters, and security schemes. This tool recognizes both: operations list from paths, and the schema sidebar lists components.schemas or definitions depending on version.

How to use this OpenAPI viewer (step by step)

  1. Paste your specification or click Load sample to see a minimal Pet-style API. Alternatively use Upload to read a file from disk (common extensions: .yaml, .yml, .json).
  2. Click Parse spec. Fix any YAML or JSON syntax error the parser reports, then run again until the explorer appears.
  3. Read the info block (title, version, description) and, for OpenAPI 3, servers URLs.
  4. Under Operations, pick a row: each line is an HTTP method plus path. The detail panel shows summary text, operationId, a parameters table, request body (OpenAPI 3), responses, and full JSON for copy-paste.
  5. Open Schemas to inspect shared models. Use Copy on the input or Copy JSON in the panel when you need snippets for issues or Slack.

API design, QA, and cross-team workflows

Product and platform teams often circulate an OpenAPI contract before coding stabilizes. Viewing the spec in a structured layout reduces back-and-forth about which query parameters are required and which status codes return bodies. When you debug live traffic, map status codes using our HTTP status code reference and confirm Content-Type choices with the MIME type lookup. Together, these utilities support a complete API documentation and troubleshooting loop without leaving the site.

Related API and developer tools

Explore the full API developer toolbox for builders, formatters, and references. Highlights:

  • HTTP Request Builder — Test, document, and debug APIs without leaving the browser—pick method, headers, and body, then send with fetch.
  • API Response Formatter — Paste any JSON or XML API response: pretty-print, validate, and explore a collapsible tree view.
  • Webhook Payload Tester — Practice webhook debugging client-side: log sample POST bodies locally (e.g. localStorage) when a public capture URL is not available.
  • HTTP Status Code Reference — Search HTTP status codes with plain-English meanings, typical causes, and what to do next.
  • MIME Type Lookup — Map filenames or extensions to MIME types for Content-Type headers, uploads, and API contracts.
  • OAuth 2.0 Flow Visualizer — Walk through the authorization code flow step by step with interactive fields and diagrams.
  • API Rate Limit Calculator — Given X requests per minute and a daily budget of Y calls, see pacing and when you hit the wall.

Frequently asked questions

What is an OpenAPI or Swagger viewer?
An OpenAPI viewer reads an API description file—usually OpenAPI 3.x (formerly Swagger) in YAML or JSON—and presents paths, HTTP methods, parameters, request bodies, responses, and reusable schemas in a structured layout. It helps you review contracts, onboard teammates, and sanity-check documentation without installing desktop tools.
Is my OpenAPI document uploaded to your servers?
No. Parsing and rendering run entirely in your browser. The specification stays in your tab unless you navigate away or use other tools on this site that intentionally call external APIs.
Does this support Swagger 2.0 and OpenAPI 3.x?
Yes. The tool detects Swagger 2.0 via the swagger: "2.0" field and OpenAPI 3.x via an openapi field starting with 3. Paths, operations, and schema maps (definitions for Swagger 2, components.schemas for OpenAPI 3) are shown accordingly.
Can I load a file instead of pasting?
Use Upload to pick a .yaml, .yml, or .json file from disk. The contents appear in the editor so you can parse and browse the same way as pasted text.
How are $ref pointers handled?
Internal JSON Pointer references that start with #/ are resolved when you open path items that use $ref, and when displaying schema bodies. External URL references are not fetched for privacy and network reasons—those remain as raw $ref strings in the JSON view.
Why does parsing fail on my YAML?
Common issues include mixed tabs and spaces, duplicate keys, or YAML anchors your parser in another tool accepted but js-yaml flags. JSON mode must be valid JSON (double quotes, no trailing commas). Fix syntax using the reported error, or validate the file in your editor first.
How is this different from Swagger UI?
Swagger UI focuses on interactive try-it-out calls against servers. This viewer is read-only documentation navigation: quick structure, parameters, and schema inspection in the browser—ideal for review and learning. For live HTTP testing, pair it with our HTTP Request Builder when you are ready to send real requests.
Can I copy parts of the spec?
Use Copy on the input to copy the full raw document. In the detail panel, copy JSON for the selected operation or schema to paste into tickets, Slack, or other tools.