IDs

Placemark supports an id for every feature. This is in accordance with the GeoJSON “id” member, which can either be a string or a number value. It’s recommended that ids are unique, but this isn’t enforced, because GeoJSON documents with duplicate ids are valid.

Formats

• id properties in incoming GeoJSON data are preserved.
• Export to KML, GeoJSON, and GeoJSONL formats will maintain IDs.

System IDs

Every feature also has a system ID, which is guaranteed to be unique across all of Placemark: this is a UUID. System IDs can’t be updated or controlled - they’re created when features are added. You can use system IDs in order to refer to features at the API level - every feature has its own endpoint in the REST API.

You can optionally include System IDs in GeoJSON exports by selecting the option in the export dialog.

User vs System IDs

User IDs:

• Can be set to any string or number value that you want.
• Are at the root level of features and are not in the properties object, so you can have both an ID on the feature and an “id” property.
• Can be imported & exported and are preserved.

System IDs:

• Are fixed and not editable.
• Can be used in Placemark’s APIs to specify a particular feature.
• Are in the properties object when they’re exported: they are the property “@id”.

Example