OpenAPI Viewer & Swagger Viewer

Paste or fetch an OpenAPI 3.x or Swagger 2.0 spec - browse endpoints, schemas, and parameters with method-colour badges.

Last reviewed: April 2026
Reviewed by , software engineer · last updated April 2026

New to this tool? Click here for instructions

Paste OpenAPI Spec (JSON or YAML)
Paste an OpenAPI spec and click Parse & View.

Quick Answer

An OpenAPI (Swagger) viewer renders a raw OpenAPI or Swagger spec into readable, interactive API documentation — showing endpoints, parameters, request bodies, and response schemas. Paste your JSON or YAML spec above (OpenAPI 3.x or Swagger 2.0) to browse it instantly. Everything runs in your browser; your spec is never uploaded to a server.

How to Use the OpenAPI Spec Viewer

The OpenAPI Spec Viewer is a free online tool that allows you to view and analyze OpenAPI 3.x and Swagger 2.0 specifications. To use the tool, simply paste your OpenAPI JSON or YAML spec into the Paste tab or enter a public URL that returns an OpenAPI spec in the URL tab. Once you have parsed your spec, you can browse endpoints, filter by method, and view detailed information about each endpoint, including parameters, request bodies, and responses. Additionally, the Analyze mode provides a quality audit of your API spec, highlighting any missing descriptions or incomplete parameters.

When to Use the Tool in Real Workflows

The OpenAPI Spec Viewer is ideal for developers who need to understand and analyze API specifications. It is particularly useful when working with third-party APIs or when designing and documenting your own APIs. By using this tool, you can quickly identify any issues or inconsistencies in your API spec, ensuring that your API is well-documented and easy to use.

How It Works

The OpenAPI Spec Viewer works by parsing the OpenAPI JSON or YAML spec that you provide. Once the spec is parsed, the tool displays a list of all endpoints in your API, along with detailed information about each endpoint. The tool also provides an Analyze mode that allows you to perform a quality audit of your API spec, highlighting any issues or inconsistencies. The tool is 100% client-side, meaning that your data is never sent to a server, ensuring that your data remains private and secure.

Tips, Edge Cases, or Limitations

When using the OpenAPI Spec Viewer, it is important to ensure that your API spec is well-formed and valid. If your spec contains errors or inconsistencies, the tool may not be able to display the information correctly. Additionally, the tool may not be able to handle very large API specs, as it is a client-side tool and may be limited by the performance of your browser.

Frequently Asked Questions

OpenAPI is a standard JSON/YAML format for describing REST APIs - all endpoints, parameters, request bodies, responses, schemas, and auth. It enables automated docs, SDK generation, mock servers, and contract testing.
OpenAPI 3.0 restructured the spec: definitions became components/schemas, host/basePath became servers, and request bodies got a dedicated requestBody field. OpenAPI 3.1 fully aligns with JSON Schema 2020-12.
Yes. Paste JSON or YAML - the tool auto-detects the format. The YAML parser handles common OpenAPI syntax: nested mappings, block sequences (arrays of objects like parameters and servers), inline flow collections such as [a, b] and {x: 1}, multi-line block scalars (| and >), and typed scalars. For specs that rely on YAML anchors and aliases, convert to JSON first.
No. All parsing and rendering happens 100% in your browser. Your spec - which may contain internal endpoint names and schemas - never leaves your machine.
Analyze shows: total endpoints by method, a list of all component schemas, endpoints missing descriptions or summaries, and paths without response definitions - a quick quality audit.