Create Transaction with Metadata (CIP-20)

Adding human-readable messages to transactions (CIP-20)

Overview

Sometimes you want to attach a message, comment, or memo to a Cardano transaction—whether it's a receipt reference, a note for future auditing, or just user-friendly text. CIP-20 standardizes how these messages appear on-chain by using label 674 in transaction metadata. With the Anvil API, you can easily attach messages to your transactions with minimal configuration.

The Anvil API lets you supply a simple message or array of messages. Under the hood, Anvil auto-formats them for CIP-20 compliance:

• Single string → ["Your message"]

• Array of strings → ["Line 1", "Line 2"]

• Long string → Automatically split across multiple array entries if it exceeds 64 bytes

For more information on transactions, please refer to the Transaction Overview.

Key Features

• Simple message attachment to transactions

• Automatic CIP-20 compliance formatting

• Support for single strings or arrays of strings

• Automatic handling of messages exceeding 64 bytes

Requirements

• A Cardano wallet with sufficient ADA

• Valid API key for authentication

Full Examples

Using Bash and cURL

Bash & cURL

Using TS/JS Fetch

Deno & Fetch

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Specifications

API Endpoint

POST /transactions/build

Request Structure

{
  "changeAddress": "<sender_address>",
  "message": "Your message" // String or array of strings
}

CIP-20 Formatting

The Anvil API automatically formats your messages for CIP-20 compliance:

• Single string → ["Your message"]

• Array of strings → ["Line 1", "Line 2"]

• Long string → Automatically split across multiple array entries if it exceeds 64 bytes

Best Practices

• Keep messages concise and relevant

• Consider privacy implications of on-chain messages

• Test transactions on testnet before moving to mainnet

• Remember that all on-chain metadata is publicly visible

• Keep your API key secure and never expose it in client-side code