Understanding Smart Contract Proxies: Transparent vs UUPS


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Understanding Smart Contract Proxies: Transparent vs UUPS


Proxies are essential in smart contract development for Ethereum and other blockchains, allowing contract upgrades without redeployment. Understanding the differences between Transparent and UUPS (Universal Upgradeable Proxy Standard) proxies is crucial for selecting the right approach.

Transparent Proxies

How They Work

  • Storage of Implementation Address: Transparent proxies store the address of the implementation contract in their storage.

  • Call Forwarding: They forward calls to the implementation contract.

Upgrade Process

  • Admin Involvement: The admin updates the implementation contract address using the upgrade() function.

  • Storage Update: The proxy updates its storage to point to the new implementation.


  • Simplicity: They are easier to understand and implement.

  • Admin-Centric Upgrades: Upgrades are centrally managed by an admin.

UUPS Proxies

How They Work

  • Use of Logic Contract: Utilizes a logic contract containing all the code.

  • Call Forwarding: All calls are forwarded to the logic contract.

Upgrade Process

  • Deploying New Logic Contract: Deploy a new logic contract first.

  • Proxy Upgrade Function: Call upgrade() on the proxy, passing the new logic contract address.

  • Indirect Storage Update: The logic contract dictates the upgrade logic, indirectly influencing the proxy storage.


  • Flexibility: Offers more flexibility in upgrades.

  • Complexity: More complex than transparent proxies.

  • Enhanced Security: Generally offers better security features.

Comparison Table: Transparent vs UUPS Proxies

FeatureTransparent ProxyUUPS Proxy
Upgrade ProcessAdmin calls upgrade() with new implementation contract address.Proxy forwards calls to a logic contract with self-contained upgrade logic.
Gas OverheadHigher due to extra storage and admin management steps.Lower as the logic is embedded within the contract itself.
FlexibilityLess flexible as upgrades are admin-driven and depend on external contract changes.More flexible, allowing for a variety of upgrade patterns and logic contained within the contract itself.


Choosing between Transparent and UUPS proxies depends on your project's needs. While Transparent proxies are simpler, UUPS proxies offer more flexibility and security. Generally, UUPS proxies are recommended unless there's a specific reason to choose Transparent proxies. Proxies, overall, provide a powerful means to make smart contracts upgradeable and adaptable over time.