Free OpenAPI Viewer & Swagger Spec Explorer

The OpenAPI Spec Viewer is a free online tool that parse and explore openapi/swagger specs with endpoint browsing, schema inspection, and curl generation. It runs entirely in your browser with no installation or sign-up needed.

OpenAPI 3.x and Swagger 2.0 in both JSON and YAML. Auto-detects format.

Export as JSON or YAML regardless of input format. Copy full spec to clipboard.

Click any endpoint, use Copy as cURL. Generates command with server URL, method, headers, and body placeholders.

Yes, the OpenAPI Spec Viewer is 100% free with no registration, no hidden fees, and no usage limits. All processing happens locally in your browser, ensuring complete privacy.

Absolutely. The OpenAPI Spec Viewer processes everything client-side in your browser. No data is uploaded to or stored on any server. Your content remains private on your device at all times.

Yes, the OpenAPI Spec Viewer is fully responsive and works on smartphones and tablets. You can use it on any device with a modern web browser -- no app download required.

No account or registration is needed. Simply open the OpenAPI Spec Viewer in your browser and start using it immediately. There are no sign-up walls or usage restrictions.

The OpenAPI Spec Viewer supports a wide range of popular formats and languages. Check the tool interface for the full list of supported options.

Simply enter your input in the provided field, adjust any settings to your preference, and the tool will process it instantly. You can then copy the result to your clipboard or download it.

Swagger was the original name for the specification, and version 2.0 is still widely called "Swagger." In 2016 the format was donated to the OpenAPI Initiative and renamed OpenAPI, so version 3.x is properly called OpenAPI. Today "Swagger" usually refers to the tooling — Swagger UI, Swagger Editor, Codegen — while "OpenAPI" refers to the specification document itself. The two are the same family: both describe a REST API's endpoints, parameters, request bodies, responses, and data models in a single JSON or YAML file. The main structural change in 3.x is that body parameters and response models moved into a reusable "components/schemas" section, and "definitions" became "schemas." This viewer reads both Swagger 2.0 and OpenAPI 3.x, detecting which version your document uses and rendering it the same way, so paste either format to explore it.

Yes. Because the viewer parses your specification into a structured object in memory, it can hand the same document back in either serialization format regardless of how you pasted it. Drop in a YAML spec and use Export JSON to download a properly formatted JSON version, or paste JSON and use Export YAML to get the indented YAML equivalent — the API description, endpoints, and schemas stay identical, only the syntax changes. This is handy when a build tool, mock server, or client generator expects one format but your team authored the spec in the other. You can also copy the whole converted document straight to your clipboard. All of it runs locally in your browser, so even an internal or unpublished spec never leaves your machine. Paste your file and pick the export format you need.

The format is detected automatically from the first non-whitespace character. If your pasted text begins with an opening brace, it is treated as JSON and parsed accordingly; anything else is parsed as YAML, since valid JSON for a spec always starts with an object. After parsing, the viewer checks for an "openapi" or "swagger" field to confirm the document is a genuine specification rather than arbitrary data. If parsing fails — a stray tab, a missing quote, bad indentation — it shows the exact error message instead of a blank screen, so you can find and fix the problem fast. This means you never have to tell it which format you are using or strip comments first. Just paste the raw contents of your spec file and the viewer figures out the rest, then renders the API for you.

OpenAPI specs avoid repetition by defining models once under "components/schemas" and pointing to them elsewhere with "$ref" references — a response might reference a Pet schema that itself references a Category and an array of Tags. In the Schemas tab, the viewer renders each model as an expandable tree and resolves those "$ref" pointers to the model they target, so you can click through nested objects and arrays instead of scrolling through raw text hunting for definitions. Every property shows its type, format, whether it is required, and any enum options, which makes the real shape of each model clear at a glance. That saves you from manually cross-referencing one part of the file against another to understand how the data fits together. Open the Schemas tab after parsing your spec to walk the model relationships visually.

Color coding is a readability aid that lets you scan a large API without reading every label. Each operation carries a method badge — GET, POST, PUT, PATCH, DELETE, HEAD, OPTIONS — colored by verb, so safe reads stand out from writes and deletes when you skim a long list of endpoints grouped by tag. Inside an expanded endpoint, response status codes are colored by class: 2xx success, 3xx redirects, 4xx client errors, and 5xx server errors are each distinguishable at a glance, so you can immediately see which responses an operation can return. Deprecated operations are flagged separately so you do not build against an endpoint that is on its way out. Together these cues turn a dense spec into something you can triage quickly. Paste a spec, or load the built-in Petstore sample, to see the color scheme in action.