monero-site/knowledge-base/moneropedia/paymentid.md

---
layout: moneropedia
entry: "Payment ID"
terms: ["payment-ID", "payment-IDs"]
summary: "an optional flag that is added to identify transactions to merchants, consisting of 64 hexadecimal characters"
---

### The Basics

Payment ID is an **arbitrary** and **optional** transaction attachment that consists of 32 bytes (64 hexadecimal characters).

It is usually used to identify transactions to merchants and exchanges: Given the intrinsic privacy features built into Monero, where a single public address is usually used for incoming transactions, the Payment ID is especially useful to tie incoming payments with user accounts.

### Creating a Payment ID
One can create a Payment ID quickly from the command line using OpenSSL:

```# openssl rand 32 -hex```
fixed getting-started link on home, added 3 moneropedia entries 2015-02-23 14:58:51 +00:00			`---`
			`layout: moneropedia`
			`entry: "Payment ID"`
			`terms: ["payment-ID", "payment-IDs"]`
Don't capitalize page summaries 2015-04-26 09:04:16 +00:00			`summary: "an optional flag that is added to identify transactions to merchants, consisting of 64 hexadecimal characters"`
fixed getting-started link on home, added 3 moneropedia entries 2015-02-23 14:58:51 +00:00			`---`

			`### The Basics`

Update paymentid.md A bit more information about Payment ID's 2015-04-25 16:07:21 +00:00			`Payment ID is an arbitrary and optional transaction attachment that consists of 32 bytes (64 hexadecimal characters).`

			`It is usually used to identify transactions to merchants and exchanges: Given the intrinsic privacy features built into Monero, where a single public address is usually used for incoming transactions, the Payment ID is especially useful to tie incoming payments with user accounts.`

			`### Creating a Payment ID`
			`One can create a Payment ID quickly from the command line using OpenSSL:`

			```# openssl rand 32 -hex```