> ## Documentation Index
> Fetch the complete documentation index at: https://docs.gr4vy.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Card fingerprints

> A unique hash for every card in the vault

A card fingerprint can be used to seamlessly identify card numbers stored in your vault without the burden of PCI compliance.

Key features of card fingerprints.

* Secure and irreversible fingerprint generation for every card received by the system
* Inclusion of fingerprint values in API responses wherever payment methods are returned, ensuring seamless integration with your system

## Use-cases

There are a few use cases for card fingerprints.

1. Identifying fraud: Because the API does not return the original raw card number back via the API, it's hard to know if a card
   has been used previously in a fraudulent transaction. For example, two transactions with the same masked card number of
   `4111 11** **** 1111` could be the same number or two different numbers.
2. Identifying duplicate cards: Similarly, you could use the card fingerprint to determine if the same card is stored twice for a user
   without needing to see the original number.

## Availability & limitations

A card `fingerprint` is returned for every `payment_method` returned by the API. Fingerprints are the same for every unique card number used.
Because of this, payments made with Apple Pay, Click to Pay, and some Google Pay have a different fingerprint than cards filled in by hand by your
customers.

## Comparison to PAR

[PAR](./payment-account-reference.mdx) and fingerprints go hand in hand to detect duplicate and fraudulent cards.

* PAR has limited availability and depends on the data received back from the payment service, while card fingerprints are available for every card transaction
* PARs represent the underlying account, while a fingerprint represents the actual card number. As a result, the fingerprint is different when using a digital wallet like Apple Pay or Google Pay.