One-Time Approval

What is One-Time Approval

Matcha Meta was built by the team behind 0x, a leading DEX aggregator. Over the years, users have trusted 0x smart contracts with billions of dollars in token approvals.

One-Time Approval allows users to reuse their existing approvals to 0x smart contracts and trade across any aggregator without granting new approvals each time.

Security Benefits of One-Time Approval

One-Time Approval is designed to reduce approval risk and limit trust exposure.

• Single Trusted Approval Surface

  • Instead of approving tokens to multiple aggregator contracts, users approve a single 0x contract called AllowanceHolder, which routes trades across aggregators.

• Reduced Smart Contract Trust Exposure

  • At-rest funds: Without One-Time Approval, users must grant token approvals directly to each aggregator they trade through. This requires trusting each aggregator’s smart contracts individually.

  • In-flight funds: Without One-Time Approval, users implicitly trust each aggregator’s contracts to respect their slippage limits. When One-Time Approval is enabled, 0x settlement contracts enforce the user’s slippage limit and revert the transaction if it is exceeded.

• Audited and Widely Reviewed Infrastructure

  • The AllowanceHolder contract has undergone multiple external security audits.

• Battle-tested at Scale

  • The broader 0x smart contract infrastructure is battle-tested at scale:

    • Over $60 billion in trading volume processed

    • Over 800,000 wallets have active approvals on Ethereum

    • Over 965,000 wallets have active approvals on Base

In addition to Matcha Matcha, the 0x AllowanceHolder contract is integrated by leading wallets including Coinbase, Phantom, and Trust Wallet. As a result, it is one of the most widely used token approval contracts in the ecosystem.

By consolidating approvals into a single, extensively audited contract, One-Time Approval reduces the number of contracts that can access your tokens.

The "Whack-a-Mole" Approval Problem

On many meta aggregators, token approvals must be granted separately to each underlying aggregator contract.

For example:

• Odos has the best quote → you approve Odos

• Quotes refresh → 1inch becomes best → you approve 1inch

• Quotes refresh again → another aggregator becomes best → repeat

This creates a frustrating and repetitive approval cycle.

If you are already comfortable trading through 0x, Matcha Meta eliminates this problem. With One-Time Approval, you approve once and trade across aggregators without repeating the process.