espocrm-base/application/Espo/Resources/metadata/fields/url.json

{
   "params":[
      {
         "name":"required",
         "type":"bool",
         "default":false
      },
      {
         "name":"default",
         "type":"varchar"
      },
      {
         "name":"maxLength",
         "type":"int"
      },
      {
         "name":"audited",
         "type":"bool"
      }
   ],
   "filter": true,
   "fieldDefs":{
      "type":"varchar"
   }
}