API Response Tester
Send HTTP requests and inspect response status, headers, timing, and body.
Request
Content-Type
Headers
Body
BuildStudio API Tester vs Postman vs Insomnia vs Bruno vs Hoppscotch
| BuildStudio | Postman | Insomnia | Bruno | Hoppscotch | |
|---|---|---|---|---|---|
| Install required | No (browser) | Yes (desktop app) | Yes (desktop app) | Yes | No (browser) |
| Signup required | No | Yes (free tier) | Yes | No | Optional |
| Cloud sync | No (by design) | Yes | Yes | Git-based | Yes (optional) |
| Free tier limits | Unlimited | 3 collaborators, 25 runs/mo | Limited collections | Unlimited (open source) | Unlimited (open source) |
| Environment variables | URL hash | Yes | Yes | .env files | Yes |
| Pre-request scripts | Static body only | Yes (JS) | Yes | Yes | Yes |
| WebSocket testing | No | Yes | Yes | Yes | Yes |
| GraphQL | No | Yes | Yes | Yes | Yes |
| Browser CORS handled | Respected | Bypassed (native request) | Bypassed | Bypassed | Proxy option |
| Best for | Quick ad-hoc checks, inspecting responses, shareable URLs | Team workflows, test suites | Full-feature dev | Git-versioned API specs | Browser-first dev |
BuildStudio isn't trying to replace Postman for team workflows. It's the right tool when you want to fire a request right now, inspect the response, share the request URL with a teammate, and walk away — no account, no install, no commitment.
Debugging a CORS error on your API
If BuildStudio's tester returns a CORS error but curl works fine, the API is blocking browser origins. This is different from "the API is broken" — the API is working, it's just rejecting browser requests by design.
Diagnostic path:
- Test with our CORS Tester to see which origins the API explicitly allows. If your browser origin isn't in the
Access-Control-Allow-Originlist, that's the problem. - For your own API: add CORS headers. Express:
app.use(cors({ origin: 'https://buildstud.io' })). ASP.NET:app.UseCors(policy => policy.WithOrigins("https://buildstud.io")). nginx:add_header Access-Control-Allow-Origin 'https://buildstud.io' always;. - For a third-party API you don't control: use
curl, Postman, or server-side scripting instead. Browsers can't bypass CORS without the server cooperating.
CORS is a browser security feature, not a server one. The server can't know your browser is making the request from buildstud.io — it just sees an Origin header that your browser added automatically. The browser refuses to show you the response if the server's Access-Control-Allow-Origin doesn't match.
Frequently Asked Questions
Is this a free online API tester like Postman?
Yes. Our API tester runs fully in your browser — send GET, POST, PUT, DELETE, PATCH and custom HTTP requests with headers, body and query params, and view the full response. No signup, no install, no paid tier like Postman or Insomnia.
How do I test a REST API without installing software?
Paste the endpoint URL, pick an HTTP method, add headers or a JSON body, and hit Send. The tester renders status code, response headers, timing and pretty-printed body in the browser. It's the fastest way to test a REST API online.
Can I send authenticated API requests with Bearer tokens or Basic auth?
Yes. Add an Authorization header with `Bearer <token>` for JWT/OAuth APIs, or `Basic <base64>` for Basic auth. Your credentials never leave the browser — every request is made client-side.
Does the API tester support CORS-protected endpoints?
Browser security blocks cross-origin requests that don't set CORS headers. If you hit a CORS error, use our CORS Tester tool to check which origins the API allows, or run the request server-side. Our tester honours browser CORS policy for safety.
Can I save or share an API request?
Every request is URL-encoded into the page hash, so the full request (URL, method, headers, body) can be bookmarked or shared. Nothing is stored on our servers — it's all client-side.
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