API Tester Playground
Test REST APIs, bypass CORS, and inspect JSON responses instantly.
Request Configuration
Response
What is this Free API Testing Tool?
The API Tester is a lightweight, browser-based alternative to Postman: send GET, POST, PUT, PATCH and DELETE requests, set headers and JSON bodies, and inspect status codes, response times and formatted output.
A built-in proxy mode routes requests through a backend server, which lets you test public APIs that would otherwise be blocked by browser CORS restrictions. Toggle it off to hit localhost APIs directly.
The tool is suited to focused endpoint checks rather than full automated test suites. Response timing includes network and proxy overhead, and requests that modify data should be aimed at safe development or staging environments.
How API Tester Playground works in practice
- 1Select the HTTP method and enter the endpoint URL.
- 2Toggle "Proxy Mode" on for public APIs (bypasses CORS), or off for localhost APIs.
- 3Add headers (like Authorization tokens) and a JSON body if needed.
- 4Click Send Request and review the status code, response time and formatted response.
Jobs this tool is built for
- Verify the status and JSON shape of a new GET endpoint during development.
- Send a sample POST or PATCH body to a staging API while debugging validation.
- Check whether an Authorization header and token are accepted by a public service.
- Compare direct localhost behavior with proxy mode when investigating a CORS failure.
What you can do here
- CORS-bypass proxy for public APIs
- Direct mode for localhost development servers
- GET, POST, PUT, PATCH and DELETE support
- Custom headers and JSON request bodies
- Syntax-highlighted, formatted JSON responses
Limits and honest caveats
- The proxy forwards requests and streams responses back without storing or logging headers, bodies or responses.
- File attachments in multipart requests are limited to 1MB each.
Common questions about API Tester Playground
Why do I need a CORS proxy?
Browsers block cross-origin JavaScript requests unless the target server allows them. The proxy makes the request server-side, where CORS rules do not apply.
Can I test my localhost API?
Yes — toggle Proxy Mode off so the request originates from your browser and can reach your local machine.
Should I paste production credentials?
Avoid long-lived production secrets in any online tester. Prefer short-lived development tokens and non-production endpoints, especially when proxy mode forwards the request through a backend.
Is response time a benchmark?
No. It is useful for a quick comparison, but browser, network and proxy overhead make it unsuitable as a controlled performance benchmark.
This page was written by the ToolSink team to explain how API Tester Playground works on this site — it is not syndicated, scraped, or spun from another publisher. How we write tool guides · Site updates · About ToolSink.
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