Auto-incrementing integer/ID field (at AGOL feature layer level)

Bud

This idea is to create an auto-incrementing integer field using the AGOL UI. The mechanism would be at the AGOL feature layer level, not at the app level, so it can be used globally.

The OBJECTID field isn't suitable because it can't be used everywhere, such as for copy/pasting features in the Experience Builder editor widget. Further, it's generally considered unwise to rely on OBJECTIDs.

Related AGOL Question: Auto-populate unique ID field in hosted feature layer (common ID between copy/pasted features in ExB)

Bud

@JonathanMcD, you might like @MobiusSnake’s comment in Add GUID field to existing AGOL Survey123 feature layer — Field not auto-populating?

GUID fields don't autopopulate, they default to null.  They're typically up to the application or an editor to set.

You could make a hidden field in your S123 form for the question and use the uuid() function to populate it.

Alternatively, you can use the Admin REST API to create the field with a NEWID() default value, with the Add to Definition endpoint of the layer.  It may be possible to update an existing field's default value with this as well, but I haven't tried it.  This will make the field autopopulate with a new value in the same way that Global IDs are autopopulated:

{
  "fields":
  [
    {
      "name" : "MyID", 
      "type" : "esriFieldTypeGUID", 
      "alias" : "My ID", 
      "sqlType" : "sqlTypeOther", 
      "length" : 38, 
      "nullable" : false, 
      "editable" : false, 
      "domain" : null, 
      "defaultValue" : "NEWID() WITH VALUES"
    }
  ]
}