Open a swagger.json or swagger.yaml and browse its endpoints without uploading it
Runs in your browser. Nothing you type is sent anywhere. Checked against sources on 22 Oct 2026.Swagger 2.0 files are still everywhere, and opening one usually means pasting it into an online editor that uploads it. Here the file is read in your browser: every endpoint grouped by tag, with its parameters, the body parameter or form fields, the responses with their schemas, and the security it needs. The checks follow the Swagger 2.0 rules, such as one body parameter per operation, and OpenAPI 3.0 and 3.1 files are read too.
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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 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.
The rest of the article, and all 6 questions about OpenAPI Viewer and Validator, are on the OpenAPI Viewer and Validator page.
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.
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.
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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.