Warning: Riverside county do not have a online parcel owner checking tool. Since 2022 Riverside County do not allow public to view or download parcel owner shapefile (file geodatabase) any more. Current the only way to get parcel owner is to ask County assessor office (GIS team). They can email you download link for free. You can sign up a contract as purchase order (around $150/months) to get parcel owner monthly. Riverside county update parcel owner monthly. San Bernadio County update parcel owner bi-weekly.
San Bernadio County have 2 online parcel owner checking tool. One is on enterprise portal, one is on arcgis online open data.
This is SB county arcgis online item, hosted on arcgis.com. This is not same as the other owner checking app on county enterprise portal.
Step 1. search parcel on San Bernadio County open data
https://open.sbcounty.gov/search?collection=Dataset&q=parcel
Step 2. check owner online
https://open.sbcounty.gov/datasets/9ca3e6b812d1473fb42eafd412a16139_0/explore?location=33.964876%2C-117.691735%2C17.97
Step 3. download parcel owner shapefile
https://open.sbcounty.gov/datasets/49323ddf29ef475db75e141f675fac47/about
Step 4. use ArcPro to open parcel owner shapefile, owner is here
Step 5. open data parcel owner comes from this web service
https://services.arcgis.com/aA3snZwJfFkVyDuP/arcgis/rest/services
https://transparentgov.net/json2tree/esri/server/folder.html?org=https%3A%2F%2Fservices.arcgis.com%2FaA3snZwJfFkVyDuP%2Farcgis%2Frest%2Fservices&url=https%3A%2F%2Fservices.arcgis.com%2FaA3snZwJfFkVyDuP%2Farcgis%2Frest%2Fservices&arcgis_online_token=&select_folder=3&select_layer=0
Step 6. check parcel owner on google map
https://transparentgov.net:3200/googlemaps/default?layer_id=0&layer=Parcels¢er_lat=34.091963089289486¢er_long=-117.62820160367849¢er_zoom=20&url=https%3A%2F%2Fservices.arcgis.com%2FaA3snZwJfFkVyDuP%2Farcgis%2Frest%2Fservices%2FParcels_for_San_Bernardino_County%2FFeatureServer&overlayType=overlayType_none&panto=0
Step 7. more data on SB county open data hub
https://transparentgov.net/json2tree/esri/online/hub7.html?filter_by=&org=https%3A%2F%2Fopen.sbcounty.gov%2F&url=https%3A%2F%2Fopen.sbcounty.gov%2F