The Ludocid, sometimes referred to as the 'CID', is a unique ID that Google assigns to a specific business location in order to identify it within its systems.

The Place ID is another unique ID that Google uses to identify a specific business within its systems.

The FID is a unique ID that relates to reviews that Google holds about a specific business.

The Ludocid can be used within Google search URLs to return the Knowledge Panel for that specific business. It can also be used within Google Maps to view a specific business.

Here's an example of Ludocid in action within a Google Maps URL

There are two common uses of the Place ID. The first is in the Google Places API; passing this ID to Google can return extensive information about a business including its name, address, website URL, opening hours, etc. The second use is in constructing a Google search URL to trigger a page that displays all the reviews for a business, or the page where users can write a new review for a business. When Google sees these IDs in a URL, it automatically converts it to a different URL that combines the Ludocid with the FID.

See the Place ID in action for reading reviews and writing reviews.

The FID has fewer practical uses than the Ludocid and the Place ID, as it's primarily used in combination with the Place ID to generate a 'write reviews' or 'read reviews' URL. If you know the Place ID, then Google converts this to the FID for you, so you're unlikely to use the FID directly. It's easier to create URLs to read or write reviews using the Place ID, but we thought we'd add it here in case it's of use.