Most of my API checks are embarrassingly small. Is staging up? Does this endpoint still return the field the frontend expects? Did the auth header fix actually deploy? For work that small, opening Postman feels like bringing a truck to carry one grocery bag, and curl means fifteen seconds of remembering whether it's -H or -d that wants the quotes.
So this lives in a browser tab now: catssaymeow.org/api-client
Pick a method, paste a URL, add headers and a body if the call needs them, send. The response comes back as one readable unit: status code, timing, headers, and body, with the JSON already pretty-printed. Nothing to install, no account, no workspace to name.
One detail that earns its keep: the URL field also accepts a full cURL string. Copy a request out of a bug ticket or a browser's "Copy as cURL", paste it in, and the method, headers, and body populate themselves.
The part I actually built it for
Half the time someone wants to try an API tool, they don't have an endpoint handy. Staging is down, the ticket hasn't landed, or they're teaching someone what a 401 even is.
The Practice API covers that case. It's a mock REST API that runs client-side in the page, with seeded /users and /posts collections and one-click examples grouped by intent: read, write, delete, meta.
The examples aren't just happy paths. There's a 404 for a missing record, a 401 for a protected route without a token, a 204 with no body, an OPTIONS preflight. Every status a junior tester will meet in their first month, reproducible on demand.
And the mock is stateful within the page. POST a new user, then GET the collection, and the new record is there:
That's the difference between a demo and a practice environment. Reloading the page resets everything, so there's nothing to clean up and no way to break it for the next person.
The boring but important part
Real requests route through a server-side proxy with layered SSRF protections, rate limiting, and per-host circuit breakers, so the tool can't be pointed at internal infrastructure. Practice API requests never touch the network at all; the responses are generated in the page, and the response panel labels them "Simulated" so there's no confusion about what was real.
It works on a phone, too, which has saved me at least once when a deploy check couldn't wait for a laptop.
If a quick endpoint check is on today's list, it's at catssaymeow.org/api-client. Free, no signup, and the Practice API is there when the real endpoint isn't.