URL Query Builder

A clean form for adding, editing, and disabling query parameters one by one, with the resulting URL built live. Keys and values are run through encodeURIComponent; you can choose whether to keep spaces as %20 or fold them to + (the form-urlencoded variant). Disabled rows stay in the list but don't appear in the output — handy for stashing alternatives without losing them.

The space toggle matters more than it looks. %20 is the correct percent-encoding everywhere in a URL, while + means a space only inside application/x-www-form-urlencoded data, which is what a query string conventionally is. Most server frameworks decode both in the query, but path segments, HTTP headers and JSON bodies do not, so a + copied out of a query string into any of those places stays a literal plus sign. When in doubt, %20 is the safer of the two.

encodeURIComponent deliberately leaves !, ', (, ) and * unescaped. They are legal in a query and most servers accept them, but OAuth signatures and some strict parsers expect them percent-encoded, and a signature computed over the un-escaped form will not verify. Note also that the encoding is applied to whatever you type: pasting a value that is already encoded produces a double encoding, where %20 becomes %2520.

Repeated keys are preserved rather than merged, because the meaning of ?tag=a&tag=b is decided by the receiving application, not by the URL syntax. PHP collapses repeats to the last value unless the key ends in [], Rails and Express build an array, and Go's standard library returns only the first. If a duplicate key is not producing what you expect, the fix belongs on the server side.