Intermediate

What Is a Token Approval?

By DappAtlas editors ·

On this page

A token approval is an on-chain permission that lets a smart contract, such as a DEX, move a set amount of a specific token from your wallet. Unlimited approvals stay active until you revoke them.

Key takeaways

  • Apps need an approval before they can move your ERC-20 tokens.
  • Many apps ask for an unlimited amount by default.
  • A malicious or hacked contract can use an old approval to take tokens.
  • You can revoke approvals at any time; revoking costs a small gas fee.

How token approvals work

The ERC-20 standard has an approve function: you sign a transaction that sets how much of a token a contract may spend. The app then moves tokens up to that amount without asking again.[1]

Risks and scams

Wallet drainers trick you into approving a malicious contract, then empty that token. Approvals given to apps that are later hacked are also a risk.[2]

How to stay safe

Approve only the amount you need, read what your wallet shows before signing and revoke old approvals with a revoke tool. Wallets with transaction previews help spot bad approvals.[2]

The Bottom Line

An approval is a standing permission. Keep them small and clean up the ones you no longer use.

Educational content, not financial advice.

Self-custodyHolding your own keys instead of trusting an exchange.Gas feeWhat you pay the network to process a transaction.Private keyThe secret number that signs transactions for one address.
Pros
  • Lets apps work without asking for each transfer
Cons
  • Unlimited approvals stay active until revoked
  • The main tool of wallet drainers
Sources (2)
  1. [1] Ethereum Improvement Proposals. “ERC-20: Token Standard.” Accessed Sep 26, 2026.
  2. [2] Revoke.cash. “What are token approvals?.” Accessed Sep 26, 2026.
SecurityWallets

Token approval FAQ

Should I revoke old token approvals?

Yes, for apps you no longer use. It removes the risk that a hacked or malicious contract uses them.

Does revoking cost money?

Revoking is a transaction, so it costs a gas fee on that network.

How this page works

Sources: Ethereum Improvement Proposals, Revoke.cash. Data as of Sep 26, 2026.

How we review

Not affiliated with any project listed. Educational content, not financial advice.