# Query Parameters for Clients

For client side applications (does not apply necessarily to backend applications), query parameters should be singular 
in name. This might not seem intuitive, but scales well for adding new parameters that may never have multiple values:

 * **Right:** `country=`
 * **Wrong:** `countries=`
 
 Query parameters with multiple values should be comma-delimited:
 
 * **Right:** `country=US,GB`
 * **Wrong:** `country=US&country=GB`
 * **Wrong:** `country[]=US&country[]=GB`
 * **Wrong:** `country[0]=US&country[1]=GB`
 
#### This seems wrong. The [URLSearchParams](https://developer.mozilla.org/en-US/docs/Web/API/URLSearchParams) spec favors the array bracket format

While this is true, unfortunately our Firebase deep linking mechanism will treat repeated query parameters as 
duplicates, and only include the first.