Paste or drop an OpenAPI or Swagger file: see every endpoint by tag and every broken $ref
Runs in your browser. Nothing you type is sent anywhere. Checked against sources on 22 Oct 2026.Paste or drop an OpenAPI 3.0, 3.1 or Swagger 2.0 file in JSON or YAML and see every endpoint grouped by tag, with parameters, request bodies and responses. The structure is checked against 34 rules from the specifications, and every $ref that points nowhere is shown where it is written.
Paste your openapi.yaml or swagger.json into the box, or open or drop the file.
Read the checks: missing required fields, path parameters that are not defined, $refs that point to nothing.
Open an endpoint to see its parameters, request body, responses and security.
Filter the endpoints by path or method, and click Copy as Markdown for a table of every endpoint.
An API description is long, and the mistakes in it are small: a path parameter that is never defined, a response without a description, a $ref with a typo. This viewer reads your openapi.yaml or swagger.json in the browser, lists what is wrong, and shows the endpoints in a form you can read.
What is checked. The rules come from the OpenAPI 3.0.3, 3.1.0 and 2.0 specifications:
| Area | Rules |
|---|---|
| Top level | openapi or swagger version, info.title and info.version, paths (or components or webhooks in 3.1) |
| Paths | start with a slash; no two templates with the same shape, such as /users/{id} and /users/{name} |
| Parameters | name and in; path parameters required and matching the path; a schema or content; no duplicates |
| Operations | unique operationId; responses with valid status codes and a description |
| References | every local $ref resolves; security requirements name a defined scheme |
Warnings cover what is allowed but likely wrong, such as a version written as a number, which YAML turns from 1.10 into 1.1, or a request body on GET.
What is shown. Endpoints are grouped by tag in the order the document declares them. Each one opens to show its parameters with location and type, the request body per content type, each response with its schema and the security schemes it needs. Schemas are written compactly, so an array of pets reads Pet[] and an optional field gets a question mark. Copy as Markdown gives a table of every endpoint for a README or a ticket.
Nothing is fetched. A $ref to another file or a URL is listed with the place it appears, never requested, so an internal spec stays internal. The six example documents of the OpenAPI Initiative pass with no issue, which is part of the tests. Related tools: YAML to JSON, JSON Schema Validator, JSON Formatter.
OpenAPI 3.0 and 3.1 and Swagger 2.0, written in JSON or YAML. The version is read from the openapi or swagger field at the top, and the checks follow the rules of that version, so a missing responses object is an error in 3.0 but allowed in 3.1.
No. The file is read and checked entirely in your browser, and nothing is sent to a server, including any $ref to another file or URL, which is listed rather than fetched. Internal and unreleased API descriptions are safe to open here.
No. Every rule that matters for a working document is checked, from required fields and path parameters to broken references, but not every detail of the official JSON Schema, such as each allowed field of a Schema Object. Use it to find real mistakes fast.
Every {name} in a path needs a parameter with that exact name, in: path and required: true, either on the path or on the operation. A parameter named id does not cover {userId}, and a path parameter whose name is not in the path is an error too.
A local $ref such as #/components/schemas/User is a pointer into the same document. When no schema, parameter or response exists at that place, usually because of a typo or a renamed component, the tool shows the reference and where it is written.
Yes. Copy as Markdown, or Ctrl+Enter, copies a table for every tag with the method, path and summary of each endpoint, marked when deprecated. Paste it into a README, a wiki page or a ticket; tables render on GitHub, GitLab and most wikis.
Rates and rules change; check the source before you rely on a figure.
Still stuck? Ask about OpenAPI Viewer and Validator and anybody who knows can answer. No account needed.
Same job, other tools: Twitter Card Validator – Check twitter:card tags and the og: tags X falls back to.
On the related tools: Readability Checker – Flesch reading ease and grade level, with what to change · JSONPath Evaluator – Evaluate a JSONPath expression and get the matching values and their paths.