public Uri uri { get; set; }

The passed Uri must be full absolute URI.

This property cannot be set after calling UnityWebRequest.SendWebRequest.

If the UnityWebRequest encounters and follows redirects, this property will be updated with the URL to which the UnityWebRequest was redirected.

Same as UnityWebRequest.url, but has less validation and pre-processing, so is much faster to set. Reading it's value is, however, more expensive because the new Uri instance is created, so if you want to get the URL your request ended up to, it's recommended to use UnityWebRequest.url, unless an Uri object is what you need.