API Playground

A fake API sandbox. Send real-looking requests and see how APIs respond. No backend needed.

API Testing Best Practices

Before you start firing off API calls, you need a testing strategy. Professional developers follow a clear methodology to avoid breaking things in production and to make debugging easier when something goes wrong.

1. Start with the Docs

Every reputable API has documentation. Read it before writing a single line of code. Look for: base URL, required headers, authentication method, request/response schemas, and rate limits. Skipping the docs is the number one cause of wasted debugging time.

2. Use a Test Environment First

Most APIs offer sandbox or test modes. Stripe has test keys (sk_test_...), PayPal has sandbox accounts, and many APIs have staging URLs. Always test against these before touching production data. A single POST to a live payment endpoint with wrong data can create real charges.

3. Test One Endpoint at a Time

Do not build an entire integration and then test everything at once. Test each endpoint individually: verify the request format, check the response structure, confirm error handling. Only chain endpoints together after each one works in isolation.

4. Log Everything During Development

Print the full request URL, headers (minus secrets), request body, response status, and response body. When something fails, you need the complete picture. Remove verbose logging before going to production, but keep error logging forever.

5. Test Error Cases Intentionally

Send a request with a missing required field. Send an invalid API key. Hit a non-existent endpoint. Try to create a duplicate resource. Your code needs to handle all of these gracefully. If you only test the happy path, your automation will break the first time something unexpected happens.

HTTP Status Codes — The Complete Guide

Status codes are the server's way of telling you what happened. They are grouped into five categories by their first digit. Memorize the common ones — you will see them constantly.

2xx — Success

200 OK — The request succeeded. For GET requests, the response body contains the data you asked for. The most common success code.

201 Created — A new resource was successfully created. Returned after a successful POST request. The response usually includes the new resource with its assigned ID.

204 No Content — The request succeeded, but there is no body to return. Common after DELETE requests. The absence of a body is intentional.

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