Mint NFTs (CIP-68)

An overview of how to mint CIP-68 compliant NFTs and other native assets on Cardano using the Anvil API

What is CIP-68?

Cardano Improvement Proposal 68 (CIP-68) is a metadata standard that revolutionized how NFT metadata is managed on Cardano. It enabled truly updatable metadata after minting through a dual-token architecture, perfect for dynamic NFTs like game items, evolving collectibles, or interactive art.

Why CIP-68 Was Created

CIP-25 Limitations:

• Metadata inaccessible to smart contracts (stored in transaction metadata).

• Complex and high cost metadata updates requiring mint/burn cycles with double-mint periods.

• Metadata resolution requires scanning blockchain history to find the "last minted transaction" for each token.

• Permanent immutability once policy is time-locked.

CIP-68 Solution: A dual-token architecture separating metadata storage from ownership, enabling seamless updates, smart contract integration, and enhanced security through datum-based metadata storage. Unlike CIP-25, metadata updates remain possible even after the minting policy is time-locked, as updates are controlled by the reference token's spending script rather than the minting policy.

CIP-68 Trade-offs:

• Higher initial minting costs (requires creating two tokens instead of one)

• Increased complexity managing dual-token architecture, creating additional UTxO overhead for reference token storage.

How It Works

CIP-68 uses an innovative dual-token system where each NFT consists of two linked tokens:

• Reference Token (Label 100): Stores the updatable metadata at a script address or Admin wallet

• User Token (Label 222): Resides in the user's wallet and inherits metadata from the reference token

This separation allows metadata updates without affecting user ownership or requiring token transfers.

Validation Approaches: Native Scripts vs. Smart Contracts

CIP-68's updatable metadata is managed by a Reference Token, which can be secured in two ways:

1. Metadata-Manager Wallet with a Native Script: This approach uses a standard wallet and a native script to control the Reference Token. It's straightforward and low-cost, making it ideal for projects that don't need complex on-chain logic. The trade-off is that it relies on trusting the wallet owner to manage metadata updates and token supply correctly.

2. Smart Contract (Plutus/Aiken): This method uses a full smart contract to govern the Reference Token. While someone still needs to trigger updates, the smart contract validates critical aspects like supply limits and reference token to user token ratios on-chain, requiring less trust than the wallet approach. It enables complex rules for metadata updates, supply caps, and other on-chain logic, but is more complex and expensive to develop and interact with.

The choice between them depends on your project's need for trustless validation versus simplicity and cost-effectiveness. If you need custom smart contract development, or are not sure which option to choose, we recommend reaching out at [email protected].

Prerequisites

Before you start, make sure you have:

• Anvil API key – Get one here

• Cardano wallets – Use our wallet CLI to create them

• Basic understanding of CIP-68's two token system. See CIP-68 Standard Reference

Choose Your Approach

CIP-68 offers two main validation approaches for securing reference tokens:

Choose your approach based on your specific needs:

Criteria	Native Scripts	Smart Contracts
Validation Logic Customization	Simple signature + timelock validation	Complex programmable business rules
Metadata Updates	Manual wallet-based updates	Automated rule-based validation
Development Complexity	Low - JSON configuration	High - Aiken Development
Cardano Transaction Costs	Lower	Higher (~2x ADA)
Use Cases	Simple collections, personal projects	Gaming, DeFi, enterprise applications

All Guides

Getting Started

Native Script Minting

Smart Contract Guides

https://github.com/Cardano-Forge/anvil-api/blob/main/docs/guides/nft-and-ft/mint-nft-cip-68/smart-contract/logic.mdMint Examplehttps://github.com/Cardano-Forge/anvil-api/blob/main/docs/guides/nft-and-ft/mint-nft-cip-68/smart-contract/update-example.md

References & Further Reading

Official CIP Specifications

• CIP-68: Datum Metadata Standard - The official specification for updatable NFT metadata

• CIP-25: NFT Metadata Standard - Traditional NFT metadata standard

• CIP-86: NFT Metadata Update Oracles - Extension for CIP-25 metadata updates