---
id: luhn
title: luhn Search Operator
sidebar_label: luhn
description: Use the luhn operator to validate potential credit card numbers in log messages using Luhn's algorithm.
slug: /help/docs/search/search-query-language/search-operators/luhn/
canonical: https://www.sumologic.com/help/docs/search/search-query-language/search-operators/luhn/
---

import useBaseUrl from '@docusaurus/useBaseUrl';

The `luhn` operator uses Luhn’s algorithm to check message logs for strings of numbers that may be credit card numbers and then validates them. It takes a string as an input, strips out all characters that are not numerals, and checks if the resulting string is a valid credit card number, returning true or false accordingly.

## Syntax

`luhn(<field>) [as <field>]`

`luhn("<input string>") [as <field>]`

## Examples

### Identify and verify credit card numbers in message logs

Use the following query to identify credit card numbers in message logs, and verify them using the Luhn operator:

```sumo
| parse regex "(?<maybecc>\d{4}-\d{4}-\d{4}-\d{4})" nodrop
| parse regex "(?<maybecc>\d{4}\s\d{4}\s\d{4}\s\d{4})" nodrop
| parse regex "(?<maybecc>\d{16})" nodrop
| if (luhn(maybecc), true, false) as valid
```

which provides results such as:

<img src={useBaseUrl('img/reuse/query-search/luhn_operator_example.png')} alt="Operator example" style={{border: '1px solid gray'}} width="400" />

### Search for and verify a specific credit card number

Use the following query to search for a specific credit card number and verify it using the Luhn operator:

```sumo
*| "6666-7777-6666-8888" as b
 | luhn(b) as d
```

It would provide the following results:

<img src={useBaseUrl('img/reuse/query-search/lunh_operator_example1.png')} alt="Operator example" style={{border: '1px solid gray'}} width="400" />