Online Swagger UI
Load an OpenAPI or Swagger file from a URL, or open a local JSON or YAML file from disk, then explore the original API contract or a tester-friendly converted version in Swagger UI.
Loading Swagger UI...
Open OpenAPI And Swagger Files From URL Or Disk
Swagger UI renders an OpenAPI file as interactive API documentation. It can show endpoints, methods, parameters, request bodies, response schemas, authentication options, and request forms.
This page is useful when you want a quick online Swagger UI without installing anything. You can load a public OpenAPI URL, a local downloaded Swagger JSON file, or a local OpenAPI YAML file, then choose whether Swagger UI should use the original file or a less restrictive tester OpenAPI version. If you mainly want to export a converted file for another tool, use the OpenAPI Converter. If you want the background concepts, read the Swagger UI and Tools guide and the OpenAPI for API Testing reference.
Local files are read by your browser and rendered on the page. They are not uploaded to API Challenges.
Render A Tester OpenAPI Spec In Swagger UI
The tester profile controls convert an OpenAPI 3 file in the browser before Swagger UI renders it. The Practical profile removes common validation restrictions and adds common REST methods so you can try exploratory API requests that a strict contract might hide. The Aggressive profile adds every selectable OpenAPI method to every path and loosens generated request bodies for broader negative testing.
The conversion is a client-side approximation of the permissive OpenAPI files generated for the API Challenges hosted APIs. It can help when you are testing someone else's OpenAPI file, comparing a strict contract with real API behaviour, or preparing a less restrictive import for a REST client.
How To Use Swagger UI For REST API Testing
If this is your first time using a browser API client or Swagger UI, consider following How to Test REST APIs or the API Simulator Walkthrough first. Those tutorials show how to make requests, inspect responses, and compare tool output with the actual API behaviour.
Swagger UI is very good for discovering documented endpoints and sending normal requests. It helps you understand the available paths, required parameters, allowed request bodies, authentication options, and documented response schemas before you move into deeper exploratory API testing.
CORS Limits For Browser Swagger UI
Because this Swagger client runs in the browser, it is limited by CORS.
CORS means Cross-Origin Resource Sharing. It is the browser rule that controls whether JavaScript from one origin can call another origin. If the OpenAPI URL or the target API does not allow this site, the browser may block loading the file or block "Try it out" requests.
If a Swagger file loads but requests fail, check the API server's CORS headers and the browser developer tools network tab.
When To Use A REST Client Instead Of Swagger UI
For testing, remember that Swagger UI is driven by the OpenAPI file. If an operation is missing from the file, or the schema is strict, Swagger UI may guide you away from the invalid or unusual requests you need to test. Use the Basic Client, the REST/HTTP Clients overview, or a desktop REST client when you need more freedom.
For the API Challenges hosted APIs, we generate two OpenAPI file styles. The standard validation file describes the API as a normal user should call it. The less-validating, permissive file relaxes some schema restrictions, which makes Swagger UI and REST clients much more useful for exploratory API testing, negative testing, and trying requests that a strict OpenAPI schema might otherwise prevent.
You can compare the available files for the API Challenges OpenAPI Files, Simple API OpenAPI Files, and Buggy API OpenAPI Files. Each page links to standard validation downloads and less validation downloads for the supported OpenAPI versions.
Many REST clients can import OpenAPI files and create starter requests. Compare the API client summary reviews, or read the detailed reviews for Bruno, Postman, Insomnia, and cURL. When you need stronger evidence, combine Swagger or a REST client with an HTTP proxy to inspect the actual request and response traffic.