1:1 or 1:n isn't a one click button you switch on the user interface but a concept of biometric matching. 

1:1 (one to one) authentication means you are using 2 mode of authentication and 1:n (one to many) means you are using one mode of biometric authentication.


1:n Matching


For instance, using fingerprint only or face only would be a 1:N matching. 

This is because the scanned information will have be matched with all the users on the device/database.

Naturally, this match will take longer if there are more users in the device/database.

The match speed will show a big difference with better hardware and algorithms. This is where Suprema excels in, especially with the 2nd generation devices. 

Terminology:

In some occasions you might also hear the terms below regarding 1:n matching

Imposter matching: matching where a user that is not in the device/database scans their biometric. This will require the device/server to go through all of the users in the device/database before a match result is made


Genuine matching: matching where a user that is in the device/database scans their biometric. The match result will be made once the user is found in the device/database.


Note: 

The maximum user restriction for 1:N matching on the specification documents refers to biometric 1:N matching.

This means that the 1:N restrictions are for face only or fingerprint only modes. Using card only does not have that restriction. 





1:1 Matching


If you are using 2 modes of authentication, such Card + fingerprint or User ID + PIN, that is considered 1:1 matching. 

The first data such as user ID is searched first and then that single data is matched with the biometric data such as the fingerprint.


The benefit of this mode is that you would not have a performance impact even with a large number of users. The FA or FAR rate will be lowered as well. 


Refer to the external link below to understand the concept of 1:1 and 1:N more clearly, including the pros and cons of each modes.
Comparison of the 1:1 and 1:N authentication methods