~/tools / 11 / invalid-json-api

Malformed Payload Tester

Every client eventually meets a response that lies: a proxy truncates a body mid-array, a legacy service emits single quotes, or a load balancer returns an HTML 502 page under a application/json header. This tool serves those exact pathologies on purpose, so your response.json() catch blocks and fallback UI get tested before production does it for you. The editor will flag these payloads as invalid — here, that is the point.

compose payload

template preset

status code latency (ms)

response body — live JSON editor

— validating —

exported mock url

—

▸ open mock ↗

simulated response headers

$ man broken-json

Everything above is encoded into the #data= fragment of the exported URL — deflated and base64url-packed by your browser. Fragments are never sent to any server, so this mock is shareable and private. Paste the URL anywhere: a teammate's browser decodes it identically.

grep -i related-searches

test invalid json response
malformed json example payload
response.json() error handling test
broken api response simulator
html instead of json error