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What is a permit signature?
A permit signature is a signed message, not a transaction, that gives a spender permission to move your tokens. ERC-2612 defines it for ERC-20 tokens. It does the same job as an on-chain approval but costs the signer no gas, because anyone can submit the signature to the token contract.
What it means for you
Signing a permit costs nothing and sends nothing, so it can feel harmless, yet it lets the named spender take tokens up to the stated amount until the deadline. That is why scam sites ask for permits. The spender address, amount and deadline in the signing request are the parts to read before approving.
How it works
ERC-2612 adds a permit function to ERC-20 tokens taking an owner, spender, value, deadline and signature. The signed message is EIP-712 typed data covering owner, spender, value, a nonce and the deadline. The token contract checks the signature, the nonce and the deadline, then sets the allowance exactly as an approve call would. The motivation was that a first token action otherwise needed an account holding ETH for gas. Because anyone may submit the signature, it can be front-run, and it stays usable until it is submitted or the deadline passes.
Source: ERC-2612: Permit extension for EIP-20 signed approvals · checked 4 October 2026
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