API Response Viewer JSON
Send HTTP requests and inspect JSON responses instantly. Set custom headers, supply a request body, view formatted output with status codes and timing — free, browser-based, and no sign-up required.
What Is an API Response Viewer and Why Do Developers Need One?
REST APIs return data almost exclusively as JSON. When building or debugging an integration, you need to see exactly what a given endpoint returns — the structure, the field names, the data types, and the HTTP status code. An API response viewer JSON tool removes the need to write a throwaway script or spin up a desktop application just to inspect a single endpoint.
This tool lets you compose a full HTTP request in seconds: choose the method (GET, POST, PUT, DELETE, or PATCH), paste the URL, add any required headers such as Authorization or Accept, and supply an optional JSON body for write operations. The response is displayed with full syntax highlighting, collapsible nodes for large objects, and the HTTP status code and response time shown at a glance.
Testing REST APIs Directly in the Browser
Because this API tester runs entirely in the browser, requests are subject to the same CORS policy as any other browser-based fetch call. APIs that include permissive Access-Control-Allow-Origin headers — such as most public data APIs and APIs designed for third-party integrations — work without any configuration. Once you have the response, use the companion JSONPath Tester to extract specific values, or the Schema Generator to automatically produce a JSON Schema contract from the response you received. If the response contains malformed JSON from a buggy endpoint, paste it into the JSON Repair tool to recover a clean, valid document.
Frequently Asked Questions
What is an API response tester?
An API response tester is a browser-based tool that lets you send HTTP requests to any URL and inspect the response. You choose the HTTP method (GET, POST, PUT, DELETE, PATCH), add custom headers such as Authorization or Content-Type, supply an optional JSON request body, and then send the request. The tool displays the response status code, timing, headers, and body — with the JSON response automatically formatted and syntax-highlighted so it is easy to read and debug.
How is this different from Postman or Insomnia?
Postman and Insomnia are full desktop applications that require installation and, in Postman's case, an account. This API response viewer runs entirely in your browser with no installation or sign-up. It is ideal for quick one-off checks — verifying an endpoint returns the expected JSON, inspecting a public API, or sharing a test URL with a colleague. For complex test suites with environment variables, test scripts, and team collaboration, a dedicated desktop client remains the better choice.
Can I send POST requests with a JSON body?
Yes. Select POST (or PUT or PATCH) as the HTTP method, then paste or type your JSON payload into the request body editor. The tool automatically sets the Content-Type header to application/json if you have not already specified one. The raw JSON body is sent exactly as entered, so you can test any REST API that accepts a JSON payload.
Why do some API requests fail with a CORS error?
CORS (Cross-Origin Resource Sharing) is a browser security policy that blocks requests to a different domain unless the server explicitly allows them via CORS headers such as Access-Control-Allow-Origin. Because this tool runs in the browser, it is subject to CORS restrictions. If the API you are testing does not include the appropriate CORS headers, the browser will block the response. APIs that are designed to be called from a browser (such as public data APIs) normally allow CORS. Internal or private APIs often do not. In that case, consider using a server-side proxy or a desktop API client such as Postman to bypass this restriction.
Is it safe to send API keys or tokens through this tool?
This tool makes requests directly from your browser to the target API — no data passes through any Multi-Toolkit server. Your API keys and tokens are not logged or stored anywhere on our infrastructure. However, be aware that requests and their headers may appear in your browser's network tab. Use this tool with the same care you would take when pasting credentials into any browser-based application, and avoid using it on shared or public computers when handling sensitive credentials.