JSONPlaceholder gives you fake data. RestSimulator simulates how real APIs actually behave: slow, flaky, rate-limited, and prone to failing. That way 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 with 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 and todos, with realistic data, 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, then confirm your agent retries and recovers before it does something expensive.
Quick, browser-only tools. Convert, fix, or grab sample data, then mock it as a live API in one click.
Auto-repair common mistakes and pinpoint the exact line of any error.
sample jsonCopy, download, or fetch realistic JSON samples from a live endpoint.
yaml → jsonConvert YAML to clean, valid JSON instantly. Then mock it as an endpoint.
json → csvFlatten arrays of JSON objects into a spreadsheet-ready CSV.
json → tsGenerate TypeScript interfaces from any JSON sample.
Start hitting realistic, controllable endpoints in seconds. Free, no signup.
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