UUIDs in Blockchain: How Distributed Ledgers Handle Unique Identifiers

Introduction: Do UUIDs Belong on the Blockchain?

UUIDs are ubiquitous in traditional systems—from databases to APIs—as a way to uniquely identify resources. But in the world of blockchain, things get... a little more decentralized.

Blockchains, by design, solve many of the same problems UUIDs were created for: guaranteeing uniqueness, tracking identity, and ensuring immutability. So where do UUIDs fit in this cryptographically secure world? Let’s dig into how identifiers are managed on blockchains, and whether UUIDs still have a role to play.

How Blockchains Handle Unique Identifiers

In blockchain systems, unique identifiers are everywhere, but they don't look like traditional UUIDs. Instead, blockchains use:

• Transaction hashes: Cryptographic digests representing transactions
• Block hashes: SHA-256 hashes linking blocks in a chain
• Wallet/public keys: Unique addresses derived from elliptic curve cryptography
• Smart contract addresses: Deterministically generated from deployment context

These identifiers serve similar purposes as UUIDs—ensuring non-collision, immutability, and global uniqueness—but they are deterministic and cryptographically derived.

Example: Ethereum Transaction ID

This is essentially a cryptographic fingerprint, not a UUID—but it’s serving the same purpose.

Why Use UUIDs in Blockchain Projects?

Even if blockchains provide unique hashes, UUIDs are still useful in off-chain and hybrid applications:

• Off-chain databases: If your smart contract logs data to a traditional DB, UUIDs help maintain consistency across systems.
• Client-side session tracking: UUIDs can be used to tag user sessions interacting with a blockchain app (dApp).
• Cross-system referencing: UUIDs make excellent correlation IDs between off-chain microservices and on-chain activity.

Comparing UUIDs and Blockchain Hashes

While both offer uniqueness, blockchain IDs go a step further by ensuring verifiability and tamper-resistance.

Risks of Using UUIDs on the Chain

You might be tempted to embed UUIDs in on-chain data, but consider the following:

• Gas costs: UUIDs are 128-bit strings. Encoding them in hex or base64 increases data size—costly on Ethereum and similar blockchains.
• Redundancy: If you already have a transaction hash or address, a UUID may be unnecessary duplication.
• Determinism conflict: Blockchains value deterministic data. Random UUIDs introduce non-deterministic behavior, which can complicate consensus and testing.

Best Practices for UUIDs in Blockchain-Related Systems

• ✅ Use UUIDs off-chain to bridge blockchain data with traditional systems.
• ✅ Generate UUIDv4 or UUIDv7 identifiers client-side and link them to blockchain operations.
• ✅ Avoid using UUIDs inside smart contracts unless absolutely necessary.
• ✅ Log UUID ↔ blockchain hash pairs for audit trails and interoperability.

When UUIDs and Blockchain Work Together

Imagine you're building a decentralized supply chain tracker. Each physical item has a UUID, while every custody handoff is recorded on-chain. The UUID provides a familiar interface for external systems, while the blockchain ensures transparency and trust.

This hybrid approach is powerful—combining the openness of blockchains with the usability of UUIDs.

Conclusion: UUIDs Still Have a Place—Just Not Everywhere

Blockchains offer their own identifier mechanisms that outperform UUIDs in terms of verifiability, tamper-resistance, and immutability. But UUIDs remain incredibly valuable in the off-chain, user-facing, and interoperability layers of blockchain ecosystems.

Use them where they make sense. Let the chain handle the rest.

Further Reading

• [RFC 4122 - A Universally Unique Identifier (UUID) URN Namespace](https://www.rfc-editor.org/rfc/rfc4122)
• [Ethereum Yellow Paper](https://ethereum.github.io/yellowpaper/paper.pdf)
• [Understanding Blockchain Hash Functions](https://www.geeksforgeeks.org/blockchain-hash-functions/)