Paste a JSON object and get a ready-to-use URL query string like a=1&b=2, with every key and value percent-encoded so special characters, spaces and Unicode survive intact. Arrays become repeated keys (tags=a&tags=b) and nested objects and arrays are flattened with bracket notation (user[name]=Sam).
Go the other way too: paste a query string (with or without the leading ?) and it is decoded back into pretty-printed JSON, folding repeated keys into arrays and bracket keys into nested objects. Everything runs locally in your browser — your parameters are never uploaded to any server.