OpenAPI / Swagger Viewer — Preview a Spec Instantly
Paste an OpenAPI 3.0 or 3.1 specification in YAML or JSON and read it as documentation: endpoints, parameters, request bodies, response codes and a generated sample response for each one. The spec is parsed in your browser, so an unreleased API design never leaves your machine.
Endpoints
What OpenAPI Viewer does
An unreleased spec stays private
A specification describes an API before it ships — including endpoints that are not public yet. Parsing happens on this page with no upload, which a hosted Swagger editor cannot offer.
Faster than standing up Swagger UI
No docker run, no local server, no npm install. Paste the document and read it. That is the entire workflow.
Sample responses from the schema
Each endpoint gets a generated JSON example built from its response schema, honouring example, default, enum and string formats such as date-time and uuid.
Local $refs resolved
Shared components/schemas references are followed and merged, including allOf composition — and a self-referencing schema terminates instead of hanging the page.
Supported formats
The tool reads raw text, so whatever your stack produces will work.
How it works
Paste the specification
YAML or JSON, OpenAPI 3.0 or 3.1. The format is detected for you and parse errors name the line.
Browse the endpoints
Every method and path is listed with its summary. Expand one to see its parameters, request body and response codes.
Filter to what you need
Type in the filter box to narrow by path, method, summary, operation ID or tag — useful when the spec has hundreds of operations.
Cheatsheet
The tokens you reach for most, at a glance.
openapiVersion field — must start with 3 for this viewerpathsEach key is a URL path; each child key is an HTTP methodparametersPath-level entries apply to every operation on that pathrequestBodyReplaces the body parameter used in Swagger 2.0components/schemasShared schema definitions, referenced with $ref$refA JSON Pointer such as #/components/schemas/PetallOfComposes schemas by merging every branchoneOf / anyOfAlternative shapes; the sample uses the first branchexampleAn author-supplied value, always preferred in the sampleHow people use it
Reviewing an API design
Reading a 3,000-line YAML file in a diff is painful. Rendering it makes a missing parameter or an inconsistent response shape obvious.
Building against a new API
See the exact response shape you need to handle before writing a line of client code, and copy the sample as a test fixture.
Checking what a change did
Paste the before and after versions to see how endpoints, parameters and status codes actually differ.
Frequently asked questions
Is my specification uploaded?
No. The YAML or JSON is parsed by JavaScript on this page and never transmitted. That matters for a document that often describes endpoints and internal services before they are public.
Does it support Swagger 2.0?
No — only OpenAPI 3.0 and 3.1. A Swagger 2.0 document is detected and named as such rather than reported as invalid, so you know to convert it first.
Are external $refs resolved?
No. A reference to another file or a URL would have to be fetched, which means sending a request — and that is exactly what this tool avoids. Bundle your spec into a single document first.
How accurate is the sample response?
It reflects the schema's shape and any example, default or enum the author supplied. It is a shape preview, not real data, and it does not validate the schema.
What happens with a recursive schema?
Self-referencing schemas — tree nodes, linked lists — are legal and common. Expansion is depth-bounded and stops on a repeated reference, so the page renders instead of hanging.
Can it render a spec with hundreds of endpoints?
Yes. Endpoints render collapsed and the filter box narrows by path, method, summary, operation ID or tag, which is the practical way to navigate a large document.
Last updated 2026-08-22