JSONPlaceholder gives you fake data. RestSimulator simulates how real APIs actually behave — slow, flaky, rate-limited, failing — so your frontend and your AI agents are ready for production, not just the happy path.
No account · No API key · CORS-ready · Free
# normal request — works instantly $ curl https://restsimulator.com/api/users/1 200 OK {"id":1,"name":"Ada Lovelace", ...} # now make it misbehave — one header $ curl -H "X-Sim-Status: 503" -H "X-Sim-Delay: 3000" \ https://restsimulator.com/api/users/1 503 Service Unavailable (after 3000ms) # does your retry logic handle THAT?
Every tutorial and test suite assumes the API returns 200 OK instantly with perfect data. Production doesn't. Real APIs time out, throw 500s, rate-limit you at the worst moment, and return half-broken payloads. Most bugs that reach users live in exactly the error paths nobody tested — and you can't fix what you can't reproduce.
Add a header to make any endpoint throw errors, add seconds of latency, or fail a fraction of the time. Finally test your retries, spinners, and error states on purpose.
Users, posts, products, comments, todos — realistic data with correct status codes and CORS, ready the moment you load the page. No backend, no key.
Give agents a safe sandbox to rehearse tool calls. Inject timeouts and rate limits and confirm your agent retries and recovers — before it does something expensive.
Quick, browser-only converters. Paste your data, get a result, then mock it as a live API in one click.
Start hitting realistic, controllable endpoints in seconds — free, no signup.
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